Friday, January 29, 2010

Microsoft Visual Studio Question

1. What is Microsoft .NET?
Microsoft .NET is the Microsoft strategy for connecting systems, information, and devices through Web services so people can collaborate and communicate more effectively. .NET technology is integrated throughout Microsoft products, providing the capability to quickly build, deploy, manage, and use connected, security-enhanced solutions through the use of Web services.

 

2. What is .NET Framework?
The .NET Framework has two main components: the common language runtime and the .NET Framework class library. You can think of the runtime as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness.

The class library, is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.  

 

 The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms - for example, ASP.NET is only supported on Windows XP and Windows 2000. Windows 98/ME cannot be used for development.
IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix    web server does run on XP Home. The Mono project is attempting to implement the .NET framework on Linux

3. What is CLR?
The CLS is simply a specification that defines the rules to support language integration in such a way that programs written in any language, yet can interoperate with one another, taking full advantage of inheritance, polymorphism, exceptions, and other features. These rules and the specification are documented in the ECMA proposed standard document, "Partition I Architecture",

4. What is the CLS?
CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language.
In theory this allows very tight interop between different .NET languages - for example allowing a C# class to inherit from a VB class.


5. What does 'managed' mean in the .NET context?
The term 'managed' is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. Such code is called managed code. All C# and Visual Basic.NET code is managed by default. VS7 C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/com+).


Managed data: This is data that is allocated and de-allocated by the .NET runtime's garbage collector. C# and VB.NET data is always managed. VS7 C++ data is unmanaged by default, even when using the /com+ switch, but it can be marked as managed using the __gc keyword.Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages - for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class.

6. Is .NET a runtime service or a development platform?
Ans: It's both and actually a lot more. Microsoft .NET includes a new way of delivering software and services to businesses and consumers. A part of Microsoft.NET is the .NET Frameworks. The .NET frameworks SDK consists of two parts: the .NET common language runtime and the .NET class library. In addition, the SDK also includes command-line compilers for C#, C++, JScript, and VB. You use these compilers to build applications and components. These components require the runtime to execute so this is a development platform.

7. What are the new features of Framework 1.1 ?

  • Native Support for Developing Mobile Web Applications
  • Enable Execution of Windows Forms Assemblies Originating from the Internet
    Assemblies originating from the Internet zone—for example, Microsoft Windows® Forms controls embedded in an Internet-based Web page or Windows Forms assemblies hosted on an Internet Web server and loaded either through the Web browser or programmatically using the System.Reflection.Assembly.LoadFrom() method—now receive sufficient permission to execute in a semi-trusted manner. Default security policy has been changed so that assemblies assigned by the common language runtime (CLR) to the Internet zone code group now receive the constrained permissions associated with the Internet permission set. In the .NET Framework 1.0 Service Pack 1 and Service Pack 2, such applications received the permissions associated with the Nothing permission set and could not execute.
  • Enable Code Access Security for ASP.NET Applications
    Systems administrators can now use code access security to further lock down the permissions granted to ASP.NET Web applications and Web services. Although the operating system account under which an application runs imposes security restrictions on the application, the code access security system of the CLR can enforce additional restrictions on selected application resources based on policies specified by systems administrators. You can use this feature in a shared server environment (such as an Internet service provider (ISP) hosting multiple Web applications on one server) to isolate separate applications from one another, as well as with stand-alone servers where you want applications to run with the minimum necessary privileges.
  • Native Support for Communicating with ODBC and Oracle Databases
  • Unified Programming Model for Smart Client Application Development
    The Microsoft .NET Compact Framework brings the CLR, Windows Forms controls, and other .NET Framework features to small devices. The .NET Compact Framework supports a large subset of the .NET Framework class library optimized for small devices.
  • Support for IPv6
    The .NET Framework 1.1 supports the emerging update to the Internet Protocol, commonly referred to as IP version 6, or simply IPv6. This protocol is designed to significantly increase the address space used to identify communication endpoints in the Internet to accommodate its ongoing growth.

8.    What is Code Access Security (CAS)?
CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.

9.    . How does CAS work?
The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set.
For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.)

10. Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my ssystem it looks like this:

11. How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been added as group 1.3.1:
...
   1.3.  Zone - Internet: Internet
      1.3.1.  Site - www.mydomain.com: FullTrust
...
Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it.


12. How do I change the permission set for a code group?
Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this:
caspol -cg 1.2 FullTrust Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect.


13. Can I create my own permission set?
Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. To save you some time, here is a sample file corresponding to the 'Everything' permission set - just edit to suit your needs. When you have edited the sample, add it to the range of available permission sets like this:
caspol -ap samplepermset.xml
Then, to apply the permission set to a code group, do something like this:
caspol -cg 1.3 SamplePermSet (By default, 1.3 is the 'Internet' code group)


14. I'm having some trouble with CAS. How can I diagnose my problem?
Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol -rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol -rsp.

15. I can't be bothered with all this CAS stuff. Can I turn it off?
Yes, as long as you are an administrator. Just run:
caspol -s off

16. What is MSIL, IL?
When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Microsoft intermediate language (MSIL) is a language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.

17. Can I write IL programs directly?
Yes. Peter Drayton posted this simple example to the DOTNET mailing list:
.assembly MyAssembly {}
.class MyApp {
  .method static void Main() {
    .entrypoint
    ldstr      "Hello, IL!"
    call       void System.Console::WriteLine(class System.Object)
    ret
  }
}
Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.


18. Can I do things in IL that I can't do in C#?
Yes. A couple of simple examples are that you can throw exceptions that are not derived from System.Exception, and you can have non-zero-based arrays.

19. What is CTS?
The common type system defines how types are declared, used, and managed in the runtime, and is also an important part of the runtime's support for cross-language integration.
The common type system supports two general categories of types, each of which is further divided into subcategories:

  • Value types
    Value types directly contain their data, and instances of value types are either allocated on the stack or allocated inline in a structure. Value types can be built-in (implemented by the runtime), user-defined, or enumerations.
  • Reference types
    Reference types store a reference to the value's memory address, and are allocated on the heap. Reference types can be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values of self-describing types. Self-describing types are further split into arrays and class types. The class types are user-defined classes, boxed value types, and delegates.

20. What is JIT (just in time)? how it works?
Before Microsoft intermediate language (MSIL) can be executed, it must be converted by a .NET Framework just-in-time (JIT) compiler to native code, which is CPU-specific code that runs on the same computer architecture as the JIT compiler. Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as it is needed during execution and stores the resulting native code so that it is accessible for subsequent calls.
The runtime supplies another mode of compilation called install-time code generation. The install-time code generation mode converts MSIL to native code just as the regular JIT compiler does, but it converts larger units of code at a time, storing the resulting native code for use when the assembly is subsequently loaded and executed.As part of compiling MSIL to native code, code must pass a verification process unless an administrator has established a security policy that allows code to bypass verification. Verification examines MSIL and metadata to find out whether the code can be determined to be type safe, which means that it is known to access only the memory locations it is authorized to access.

21. What is strong name?
A name that consists of an assembly's identity—its simple text name, version number, and culture information (if provided)—strengthened by a public key and a digital signature generated over the assembly.

22. What is portable executable (PE)?
The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow them to be loaded and executed by Windows. PE is derived from the Microsoft Common Object File Format (COFF). The EXE and DLL files created using the .NET Framework obey the PE/COFF formats and also add additional header and data sections to the files that are only used by the CLR. The specification for the PE/COFF file formats is available at http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx

23. Which namespace is the base class for .net Class library?
Ans: system.object

24. What is Event - Delegate? clear syntax for writing a event delegate
The event keyword lets you specify a delegate that will be called upon the occurrence of some "event" in your code. The delegate can have one or more associated methods that will be called when your code indicates that the event has occurred. An event in one program can be made available to other programs that target the .NET Framework Common Language Runtime.
// keyword_delegate.cs
// delegate declaration
delegate void MyDelegate(int i);

class Program
{
   public static void Main()
   {
      TakesADelegate(new MyDelegate(DelegateFunction));
   }
   public static void TakesADelegate(MyDelegate SomeFunction)
   {
      SomeFunction(21);
   }
   public static void DelegateFunction(int i)
   {
      System.Console.WriteLine("Called by delegate with number: {0}.", i);
   }
}

25. What are object pooling and connection pooling and difference? Where do we set the Min and Max Pool size for connection pooling?
Object pooling is a COM+ service that enables you to reduce the overhead of creating each object from scratch. When an object is activated, it is pulled from the pool. When the object is deactivated, it is placed back into the pool to await the next request. You can configure object pooling by applying the ObjectPoolingAttribute attribute to a class that derives from the System.EnterpriseServices.ServicedComponent class. Object pooling lets you control the number of connections you use, as opposed to connection pooling, where you control the maximum number reached.  Following are important differences between object pooling and connection pooling:

  1. Creation. When using connection pooling, creation is on the same thread, so if there is nothing in the pool, a connection is created on your behalf. With object pooling, the pool might decide to create a new object. However, if you have already reached your maximum, it instead gives you the next available object. This is crucial behavior when it takes a long time to create an object, but you do not use it for very long.
  2. Enforcement of minimums and maximums. This is not done in connection pooling. The maximum value in object pooling is very important when trying to scale your application. You might need to multiplex thousands of requests to just a few objects. (TPC/C benchmarks rely on this.)

COM+ object pooling is identical to what is used in .NET Framework managed SQL Client connection pooling. For example, creation is on a different thread and minimums and maximums are enforced.

26. What is Application Domain?
The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory.
Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages.
MarshalByRefObject
is the base class for objects that communicate across application domain boundaries by exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by value. When a remote application references a marshal by value object, a copy of the object is passed across application domain boundaries.

27. How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name the executable 'appdomaintest.exe' for this code to work as-is.

using System;
using System.Runtime.Remoting;
 
public class CAppDomainInfo : MarshalByRefObject
{
   public string GetAppDomainInfo()
   {
               return "AppDomain = " + AppDomain.CurrentDomain.FriendlyName;
   }
}
public class App
{
   public static int Main()
   {
               AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null );
               ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" );
               CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap());
               string info = adInfo.GetAppDomainInfo();
               Console.WriteLine( "AppDomain info: " + info );
               return 0;
   }
}

28. What is serialization in .NET? What are the ways to control serialization?
Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database).Serialization can be defined as the process of storing the state of an object to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created.

  • Binary serialization preserves type fidelity, which is useful for preserving the state of an object between different invocations of an application. For example, you can share an object between different applications by serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth. Remoting uses serialization to pass objects "by value" from one computer or application domain to another.
  • XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful when you want to provide or consume data without restricting the application that uses the data. Because XML is an open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an attractive choice.

There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.

29. Why do I get errors when I try to serialize a Hashtable?
XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

30. What are server controls?
ASP.NET server controls are components that run on the server and encapsulate user-interface and other related functionality. They are used in ASP.NET pages and in ASP.NET code-behind classes.

31. What is the difference between Web User Control and Web Custom Control?
Custom Controls
Web custom controls are compiled components that run on the server and that encapsulate user-interface and other related functionality into reusable packages. They can include all the design-time features of standard ASP.NET server controls, including full support for Visual Studio design features such as the Properties window, the visual designer, and the Toolbox.
There are several ways that you can create Web custom controls:

  1. You can compile a control that combines the functionality of two or more existing controls. For example, if you need a control that encapsulates a button and a text box, you can create it by compiling the existing controls together.
  2. If an existing server control almost meets your requirements but lacks some required features, you can customize the control by deriving from it and overriding its properties, methods, and events.
  3. If none of the existing Web server controls (or their combinations) meet your requirements, you can create a custom control by deriving from one of the base control classes. These classes provide all the basic functionality of Web server controls, so you can focus on programming the features you need.

If none of the existing ASP.NET server controls meet the specific requirements of your applications, you can create either a Web user control or a Web custom control that encapsulates the functionality you need. The main difference between the two controls lies in ease of creation vs. ease of use at design time.
Web user controls
are easy to make, but they can be less convenient to use in advanced scenarios. You develop Web user controls almost exactly the same way that you develop Web Forms pages. Like Web Forms, user controls can be created in the visual designer, they can be written with code separated from the HTML, and they can handle execution events. However, because Web user controls are compiled dynamically at run time they cannot be added to the Toolbox, and they are represented by a simple placeholder glyph when added to a page. This makes Web user controls harder to use if you are accustomed to full Visual Studio .NET design-time support, including the Properties window and Design view previews. Also, the only way to share the user control between applications is to put a separate copy in each application, which takes more maintenance if you make changes to the control.
Web custom controls
are compiled code, which makes them easier to use but more difficult to create; Web custom controls must be authored in code. Once you have created the control, however, you can add it to the Toolbox and display it in a visual designer with full Properties window support and all the other design-time features of ASP.NET server controls. In addition, you can install a single copy of the Web custom control in the global assembly cache and share it between applications, which makes maintenance easier.

 

Web user controls

Web custom controls

 

Easier to create

Harder to create

 

Limited support for consumers who use a visual design tool

Full visual design tool support for consumers

 

A separate copy of the control is required in each application

Only a single copy of the control is required, in the global assembly cache

 

Cannot be added to the Toolbox in Visual Studio

Can be added to the Toolbox in Visual Studio

 

 

Good for static layout

Good for dynamic layout

31. What is exception handling?
When an exception occurs, the system searches for the nearest catch clause that can handle the exception, as determined by the run-time type of the exception. First, the current method is searched for a lexically enclosing try statement, and the associated catch clauses of the try statement are considered in order. If that fails, the method that called the current method is searched for a lexically enclosing try statement that encloses the point of the call to the current method. This search continues until a catch clause is found that can handle the current exception, by naming an exception class that is of the same class, or a base class, of the run-time type of the exception being thrown. A catch clause that doesn't name an exception class can handle any exception.
Once a matching catch clause is found, the system prepares to transfer control to the first statement of the catch clause. Before execution of the catch clause begins, the system first executes, in order, any
finally clauses that were associated with try statements more nested that than the one that caught the exception.
Exceptions that occur during destructor execution are worth special mention. If an exception occurs during destructor execution, and that exception is not caught, then the execution of that destructor is terminated and the destructor of the base class (if any) is called. If there is no base class (as in the case of the
object type) or if there is no base class destructor, then the exception is discarded.

32. What is Assembly?
Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.
Assemblies are a fundamental part of programming with the .NET Framework. An assembly performs the following functions:

a.    It contains code that the common language runtime executes. Microsoft intermediate language (MSIL) code in a portable executable (PE) file will not be executed if it does not have an associated assembly manifest. Note that each assembly can have only one entry point (that is, DllMain, WinMain, or Main).

b.    It forms a security boundary. An assembly is the unit at which permissions are requested and granted.

c.    It forms a type boundary. Every type's identity includes the name of the assembly in which it resides. A type called MyType loaded in the scope of one assembly is not the same as a type called MyType loaded in the scope of another assembly.

d.    It forms a reference scope boundary. The assembly's manifest contains assembly metadata that is used for resolving types and satisfying resource requests. It specifies the types and resources that are exposed outside the assembly. The manifest also enumerates other assemblies on which it depends.

e.    It forms a version boundary. The assembly is the smallest versionable unit in the common language runtime; all types and resources in the same assembly are versioned as a unit. The assembly's manifest describes the version dependencies you specify for any dependent assemblies.

f.     It forms a deployment unit. When an application starts, only the assemblies that the application initially calls must be present. Other assemblies, such as localization resources or assemblies containing utility classes, can be retrieved on demand. This allows applications to be kept simple and thin when first downloaded.

g.    It is the unit at which side-by-side execution is supported.

Assemblies can be static or dynamic. Static assemblies can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk in PE files. You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed.
There are several ways to create assemblies. You can use development tools, such as Visual Studio .NET, that you have used in the past to create .dll or .exe files. You can use tools provided in the .NET Framework SDK to create assemblies with modules created in other development environments. You can also use common language runtime APIs, such as Reflection.Emit, to create dynamic assemblies.

33. What are the contents of assembly?
In general, a static assembly can consist of four elements:

    1. The assembly manifest, which contains assembly metadata.
    2. Type metadata.
    3. Microsoft intermediate language (MSIL) code that implements the types.
    4. A set of resources.

34. What is the difference between a private assembly and a shared assembly?

Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.

Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.

35. What are Satellite Assemblies? How you will create this? How will you get the different language strings?
Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed.
(For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core runtime files.)

36. What is Assembly manifest? what all details the assembly manifest will contain?
Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest contains all the metadata needed to specify the assembly's version requirements and security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a standalone PE file that contains only assembly manifest information.
It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type reference information, Information on referenced assemblies.

37. Difference between assembly manifest & metadata?
assembly manifest -
An integral part of every assembly that renders the assembly self-describing. The assembly manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run properly. This information is used at run time to resolve references, enforce version binding policy, and validate the integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.

38. What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) How more than one version of an assembly can keep in same place?
Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer.  You should share assemblies by installing them into the global assembly cache only when you need to.
Steps
- Create a strong name using sn.exe tool
eg: sn -k keyPair.snk
- with in AssemblyInfo.cs add the generated file name
eg: [assembly: AssemblyKeyFile("abc.snk")]
- recompile project, then install it to GAC by either
drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool)
or
gacutil -i abc.dll

39. How to find methods of a assembly file (not using ILDASM)
Reflection

40. What is Partial Assembly References?

Full Assembly reference: A full assembly reference includes the assembly's text name, version, culture, and public key token (if the assembly has a strong name). A full assembly reference is required if you reference any assembly that is part of the common language runtime or any assembly located in the global assembly cache.

 

Partial Assembly reference: We can dynamically reference an assembly by providing only partial information, such as specifying only the assembly name. When you specify a partial assembly reference, the runtime looks for the assembly only in the application  directory. We can make partial references to an assembly in your code one of the following ways: -> Use a method such as System.Reflection.Assembly.Load and specify only a partial reference. The runtime checks for the assembly in the application directory. -> Use the System.Reflection.Assembly.LoadWithPartialName method and specify only a partial reference. The runtime checks for the assembly in the application directory and in the global assembly cache What is Garbage Collection in .Net? Garbage collection process?
The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.

41. Readonly vs. const?
A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used. Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants, as in the following example:
public static readonly uint l1 = (uint) DateTime.Now.Ticks;

42. What is Reflection in .NET? Namespace?  How will you load an assembly which is not referenced by current assembly?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).

43. What is Custom attribute? How to create? If I'm having custom attribute in an assembly, how to say that name in the code?
A: The primary steps to properly design custom attribute classes are as follows:

Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)])

Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })

Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })

Declaring properties 
public bool MyProperty
{
            get {return this.myvalue;}
            set {this.myvalue = value;}
}
The following example demonstrates the basic way of using reflection to get access to custom attributes. 
class MainClass 
{ 
            public static void Main() 
            { 
                        System.Reflection.MemberInfo info = typeof(MyClass);
                        object[] attributes = info.GetCustomAttributes();
                        for (int i = 0; i < attributes.Length; i ++) 
                        {
                                     System.Console.WriteLine(attributes[i]);
                        } 
            } 
} 

44 . What is the managed and unmanaged code in .net?
The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the execution of code and provides services that make the development process easier. Compilers and tools expose the runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that you develop with a language compiler that targets the runtime is called managed code; it benefits from features such as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment support, a simplified model for component interaction, and debugging and profiling services.

45. How do you create threading in .NET? What is the namespace for that?
System.Threading.Thread

46. using directive vs using statement
You create an instance in a using statement to ensure that Dispose is called on the object when the using statement is exited. A using statement can be exited either when the end of the using statement is reached or if, for example, an exception is thrown and control leaves the statement block before the end of the statement.
The using directive has two uses:

  • Create an alias for a namespace (a using alias).
  • Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that namespace (a using directive).

47. Describe the Managed Execution Process?
The managed execution process includes the following steps:

  • Choosing a compiler.
    To obtain the benefits provided by the common language runtime, you must use one or more language compilers that target the runtime.
  • Compiling your code to Microsoft intermediate language (MSIL).
    Compiling translates your source code into MSIL and generates the required metadata.
  • Compiling MSIL to native code.
    At execution time, a just-in-time (JIT) compiler translates the MSIL into native code. During this compilation, code must pass a verification process that examines the MSIL and metadata to find out whether the code can be determined to be type safe.
  • Executing your code.
    The common language runtime provides the infrastructure that enables execution to take place as well as a variety of services that can be used during execution.

48. What is Active Directory? What is the namespace used to access the Microsoft Active Directories? What are ADSI Directories?
Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft Windows Active Directory. It enables your applications to interact with diverse directories on a network, using a single interface. Visual Studio .NET and the .NET Framework make it easy to add ADSI functionality with the DirectoryEntry and DirectorySearcher components.
Using ADSI, you can create applications that perform common administrative tasks, such as backing up databases, accessing printers, and administering user accounts. ADSI makes it possible for you to:

  • Log on once to work with diverse directories. The DirectoryEntry component class provides username and password properties that can be entered at runtime and communicated to the Active Directory object you are binding to.
  • Use a single application programming interface (API) to perform tasks on multiple directory systems by offering the user a variety of protocols to use. The DirectoryServices namespace provides the classes to perform most administrative functions.
  • Perform "rich querying" on directory systems. ADSI technology allows for searching for an object by specifying two query dialects: SQL and LDAP.
  • Access and use a single, hierarchical structure for administering and maintaining diverse and complicated network configurations by accessing an Active Directory tree.
  • Integrate directory information with databases such as SQL Server. The DirectoryEntry path may be used as an ADO.NET connection string provided that it is using the LDAP provider.

using System.DirectoryServices;

49. How Garbage Collector (GC) Works?
The methods in this class influence when an object is garbage collected and when resources allocated by an object are released. Properties in this class provide information about the total amount of memory available in the system and the age category, or generation, of memory allocated to an object. Periodically, the garbage collector performs garbage collection to reclaim memory allocated to objects for which there are no valid references. Garbage collection happens automatically when a request for memory cannot be satisfied using available free memory. Alternatively, an application can force garbage collection using the Collect method.
Garbage collection consists of the following steps:

  • The garbage collector searches for managed objects that are referenced in managed code.
  • The garbage collector attempts to finalize objects that are not referenced.
  • The garbage collector frees objects that are not referenced and reclaims their memory.

50. Why do we need to call CG.SupressFinalize?
Requests that the system not call the finalizer method for the specified object.
[C#]
public static void SuppressFinalize(
   object obj
); The method removes obj from the set of objects that require finalization. The obj parameter is required to be the caller of this method.
Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it.

51. What is nmake tool?
The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based on commands contained in a .mak file.
usage : nmake -a all

52. What are Namespaces?
The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not modifiable.

53. What is Jagged Arrays?
A jagged array is an array whose elements are arrays. The elements of a jagged array can be of different dimensions and sizes. A jagged array is sometimes called an "array-of-arrays."

(COM)

54. Interop Services?
The common language runtime provides two mechanisms for interoperating with unmanaged code:

    • Platform invoke, which enables managed code to call functions exported from an unmanaged library.
    • COM interop, which enables managed code to interact with COM objects through interfaces.
  • Both platform invoke and COM interop use interop marshaling to accurately move method arguments between caller and callee and back, if required.

55. What is RCW (Runtime Callable Wrappers)?
The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object.

56. What is CCW (COM Callable Wrapper)

A proxy object generated by the common language runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently.

57. How will you register com+ services?
The .NET Framework SDK provides the .NET Framework Services Installation Tool (Regsvcs.exe - a command-line tool) to manually register an assembly containing serviced components. You can also access these registration features programmatically with the System.EnterpriseServicesRegistrationHelper class by creating an instance of class RegistrationHelper and using the method InstallAssembly

58. What is use of ContextUtil class?
ContextUtil is the preferred class to use for obtaining COM+ context information.

59. What is Pinvoke?
Platform invoke is a service that enables managed code to call unmanaged functions implemented in dynamic-link libraries (DLLs), such as those in the Win32 API. It locates and invokes an exported function and marshals its arguments (integers, strings, arrays, structures, and so on) across the interoperation boundary as needed.

60. Is it true that COM objects no longer need to be registered on the server?
Answer: Yes and No. Legacy COM objects still need to be registered on the server before they can be used. COM developed using the new .NET Framework will not need to be registered. Developers will be able to auto-register these objects just by placing them in the 'bin' folder of the application.

61. Can .NET Framework components use the features of Component Services?
Answer: Yes, you can use the features and functions of Component Services from a .NET Framework component.
(OOPS)

62. What are the OOPS concepts?
1) Encapsulation: It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and misuse. In short it isolates a particular code and data from all other codes and data. A well-defined interface controls the access to that particular code and data.
2) Inheritance: It is the process by which one object acquires the properties of another object. This supports the hierarchical classification. Without the use of hierarchies, each object would need to define all its characteristics explicitly. However, by use of inheritance, an object need only define those qualities that make it unique within its class. It can inherit its general attributes from its parent. A new sub-class inherits all of the attributes of all of its ancestors.
3) Polymorphism: It is a feature that allows one interface to be used for general class of actions. The specific action is determined by the exact nature of the situation. In general polymorphism means "one interface, multiple methods", This means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler's job to select the specific action (that is, method) as it applies to each situation.

63. What is the difference between a Struct and a Class?

  • The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive.
  • When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized.
  • It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.
  • It is an error to initialize an instance field in a struct.
  • There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.
  • A struct is a value type, while a class is a reference type.

 64. Value type & reference types difference? Example from .NET. Integer & struct are value types or reference types in .NET?
Most programming languages provide built-in data types, such as integers and floating-point numbers, that are copied when they are passed as arguments (that is, they are passed by value). In the .NET Framework, these are called value types. The runtime supports two kinds of value types:

  • Built-in value types
    The .NET Framework defines built-in value types, such as System.Int32 and System.Boolean, which correspond and are identical to primitive data types used by programming languages.
  • User-defined value types
    Your language will provide ways to define your own value types, which derive from System.ValueType. If you want to define a type representing a value that is small, such as a complex number (using two floating-point numbers), you might choose to define it as a value type because you can pass the value type efficiently by value. If the type you are defining would be more efficiently passed by reference, you should define it as a class instead.

Variables of reference types, referred to as objects, store references to the actual data. This following are the reference types: class ,interface ,delegate

This following are the built-in reference types: object ,string

65. What is Method overloading?
Method overloading occurs when a class contains two methods with the same name, but different signatures.

66. What is Method Overriding? How to override a function in C#?
Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new implementation of a member inherited from a base class. The method overridden by an override declaration is known as the overridden base method. The overridden base method must have the same signature as the override method.
You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override.

67. Can we call a base class method without creating instance?
Its possible If its a static method.
Its possible by inheriting from that class also.
Its possible from derived classes using base keyword.

68. You have one base class virtual function how will call that function from derived class?
Ans:

class a
              {
                      public virtual int m()
                      {
                                  return 1;
                      }
              }
              class b:a
              {
                      public int j()
                      {
                                  return m();
                      }
}

69. In which cases you use override and new base?
Use the new modifier to explicitly hide a member inherited from a base class. To hide an inherited member, declare it in the derived class using the same name, and modify it with the new modifier.

C# Language features

1. What are Sealed Classes in C#?
The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified as the base class of another class. (A sealed class cannot also be an abstract class)

2. What is Polymorphism? How does VB.NET/C# achieve polymorphism?

class Token
              {
                    public string Display()
                    {
                                //Implementation goes here
                                return "base";
                    }
              }
              class IdentifierToken:Token
              {
                    public new string Display() //What is the use of new keyword
                    {
                                //Implementation goes here
                                return "derive";
                    }
              }
              static void Method(Token t)
              {
                    Console.Write(t.Display());
              }
              public static void Main()
              {
                    IdentifierToken Variable=new IdentifierToken();
                    Method(Variable); //Which Class Method is called here
                    Console.ReadLine();
              }
              For the above code What is the "new" keyword and Which Class Method is
                called here

A: it will call base class Display method

class Token
              {
                    public virtual string Display()
                    {
                                //Implementation goes here
                                return "base";
                    }
              }
              class IdentifierToken:Token
              {
                    public override string Display() //What is the use of new keyword
                    {
                                //Implementation goes here
                                return "derive";
                    }
              }
              static void Method(Token t)
              {
                    Console.Write(t.Display());
              }
              public static void Main()
              {
                    IdentifierToken Variable=new IdentifierToken();
                    Method(Variable); //Which Class Method is called here
                    Console.ReadLine();
              }

A: Derive

3. In which Scenario you will go for Interface or Abstract Class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes. Even though class inheritance allows your classes to inherit implementation from a base class, it also forces you to make most of your design decisions when the class is first published.
Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code.

Interfaces vs. Abstract Classes

Feature

Interface

Abstract class

Multiple inheritance

A class may implement several interfaces.

A class may extend only one abstract class.

Default implementation

An interface cannot provide any code at all, much less default code.

An abstract class can provide complete code, default code, and/or just stubs that have to be overridden.

Constants

Static final constants only, can use them without qualification in classes that implement the interface. On the other paw, these unqualified names pollute the namespace. You can use them and it is not obvious where they are coming from since the qualification is optional.

Both instance and static constants are possible. Both static and instance intialiser code are also possible to compute the constants.

Third party convenience

An interface implementation may be added to any existing third party class.

A third party class must be rewritten to extend only from the abstract class.

is-a vs -able or can-do

Interfaces are often used to describe the peripheral abilities of a class, not its central identity, e.g. an Automobile class might implement the Recyclable interface, which could apply to many otherwise totally unrelated objects.

An abstract class defines the core identity of its descendants. If you defined a Dog abstract class then Damamation descendants are Dogs, they are not merely dogable. Implemented interfaces enumerate the general things a class can do, not the things a class is.

Plug-in

You can write a new replacement module for an interface that contains not one stick of code in common with the existing implementations. When you implement the interface, you start from scratch without any default implementation. You have to obtain your tools from other classes; nothing comes with the interface other than a few constants. This gives you freedom to implement a radically different internal design.

You must use the abstract class as-is for the code base, with all its attendant baggage, good or bad. The abstract class author has imposed structure on you. Depending on the cleverness of the author of the abstract class, this may be good or bad. Another issue that's important is what I call "heterogeneous vs. homogeneous." If implementors/subclasses are homogeneous, tend towards an abstract base class. If they are heterogeneous, use an interface. (Now all I have to do is come up with a good definition of hetero/homogeneous in this context.) If the various objects are all of-a-kind, and share a common state and behavior, then tend towards a common base class. If all they share is a set of method signatures, then tend towards an interface.

Homogeneity

If all the various implementations share is the method signatures, then an interface works best.

If the various implementations are all of a kind and share a common status and behavior, usually an abstract class works best.

Maintenance

If your client code talks only in terms of an interface, you can easily change the concrete implementation behind it, using a factory method.

Just like an interface, if your client code talks only in terms of an abstract class, you can easily change the concrete implementation behind it, using a factory method.

Speed

Slow, requires extra indirection to find the corresponding method in the actual class. Modern JVMs are discovering ways to reduce this speed penalty.

Fast

Terseness

The constant declarations in an interface are all presumed public static final, so you may leave that part out. You can't call any methods to compute the initial values of your constants. You need not declare individual methods of an interface abstract. They are all presumed so.

You can put shared code into an abstract class, where you cannot into an interface. If interfaces want to share code, you will have to write other bubblegum to arrange that. You may use methods to compute the initial values of your constants and variables, both instance and static. You must declare all the individual methods of an abstract class abstract.

Adding functionality

If you add a new method to an interface, you must track down all implementations of that interface in the universe and provide them with a concrete implementation of that method.

If you add a new method to an abstract class, you have the option of providing a default implementation of it. Then all existing code will continue to work without change.

see the code

interface ICommon
              {
                 int getCommon();
              }
              interface ICommonImplements1:ICommon
              {
              }
              interface ICommonImplements2:ICommon
              {
              }
              public class a:ICommonImplements1,ICommonImplements2
              {
}

How to implement getCommon method in class a? Are you seeing any problem in the implementation?
Ans:

public class a:ICommonImplements1,ICommonImplements2
              {
               public int getCommon()
               {
                           return 1;
               }
              }
interface IWeather
              {
                 void display();
              }
              public class A:IWeather
              {
                 public void display()
                 {
                              MessageBox.Show("A");
                 }
              }
              public class B:A
              {
              }
              public class C:B,IWeather
              {
                 public void display()
                 {
                              MessageBox.Show("C");
                 }
              }

When I instantiate C.display(), will it work?

interface IPrint
              {
                 string Display();
              }
              interface IWrite
              {
                 string Display();
              }
              class PrintDoc:IPrint,IWrite
              {
                 //Here is implementation
              }

how to implement the Display in the class printDoc (How to resolve the naming Conflict) A: no naming conflicts

class PrintDoc:IPrint,IWrite
              {
               public string Display()
               {
                           return "s";
               }
              }
interface IList
{
int Count { get; set; }
}
interface ICounter
{
void Count(int i);
}
interface IListCounter: IList, ICounter {}
class C
{
void Test(IListCounter x)
{
x.Count(1);                  // Error
x.Count = 1;               // Error
((IList)x).Count = 1;      // Ok, invokes IList.Count.set
((ICounter)x).Count(1);      // Ok, invokes ICounter.Count
}
a. }

4. Write one code example for compile time binding and one for run time binding? What is early/late binding?
An object is early bound when it is assigned to a variable declared to be of a specific object type. Early bound objects allow the compiler to allocate memory and perform other optimizations before an application executes.
' Create a variable to hold a new object.
Dim FS As FileStream
' Assign a new object to the variable.
FS = New FileStream("C:\tmp.txt", FileMode.Open)
By contrast, an object is late bound when it is assigned to a variable declared to be of type Object. Objects of this type can hold references to any object, but lack many of the advantages of early-bound objects.
Dim xlApp As Object
xlApp = CreateObject("Excel.Application")

 (Access specifiers)

5. What are the access-specifiers available in c#?
Private, Protected, Public, Internal, Protected Internal.

6. Explain about Protected and protected internal, "internal" access-specifier?
protected - Access is limited to the containing class or types derived from the containing class.
internal - Access is limited to the current assembly.
protected internal - Access is limited to the current assembly or types derived from the containing class.

(Constructor / Destructor)

7. Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?
(Class constructor method is also known as type constructor or type initializer)
Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention.
A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is created or any static members are referenced.

8. What is Private Constructor? and it's use? Can you create instance of a class which has Private Constructor?
A: When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes)
Make a constructor private if:
- You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method.
- You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory.

9. I have 3 overloaded constructors in my class. In order to avoid making instance of the class do I need to make all constructors to private?
(yes)

10. Overloaded constructor will call default constructor internally?
(no)

11. Destructor and finalize
Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over the destructors.
In C# you can never call them, the reason is one cannot destroy an object. So who has the control over the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance.
6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction.
7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to least derived.
 

12. What is the difference between Finalize and Dispose (Garbage collection)
Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object.
In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object. Dispose can be called even if other references to the object are alive.
Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose.

13. What is the use of base keyword? Tell me a practical example for base keyword's usage?

What are the different .net tools which u used in projects?

try
{...}catch{...//exception occurred here. What'll happen?}finally{..}
Ans : It will throw exception.

What will do to avoid prior case?
Ans:

try{try{...}catch{...//exception occurred here.}finally{...}}catch{...}finally{...}try{...}catch{...}finally{..}

Will it go to finally block if there is no exception happened?
Ans: Yes. The finally block is useful for cleaning up any resources allocated in the try block. Control is always passed to the finally block regardless of how the try block exits.

14. Is goto statement supported in C#? How about Java?
Gotos are supported in C#to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.

15. What's different about switch statements in C#?
No fall-throughs allowed. Unlike the C++ switch statement, C# does not support an explicit fall through from one case label to another. If you want, you can use goto a switch-case, or goto default.
case 1:
cost += 25;
break;
case 2:
cost += 25;
goto case 1;

(ADO.NET)

16. Advantage of ADO.Net?

1.    ADO.NET Does Not Depend On Continuously Live Connections

2.    Database Interactions Are Performed Using Data Commands

3.    Data Can Be Cached in Datasets

4.    Datasets Are Independent of Data Sources

5.    Data Is Persisted as XML

6.    Schemas Define Data Structures

17. How would u connect to database using .NET?
SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated Security=SSPI;" +
                                            "Initial Catalog=northwind");
nwindConn.Open();

18. What are relation objects in dataset and how & where to use them?
In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table.  Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn.
custDS.Relations.Add("CustOrders",
custDS.Tables["Customers"].Columns["CustID"],
custDS.Tables["Orders"].Columns["CustID"]);

OR

private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects in a DataSet.
DataColumn parentCol;
DataColumn childCol;
// Code to get the DataSet not shown here.
parentCol = DataSet1.Tables["Customers"].Columns["CustID"];
childCol = DataSet1.Tables["Orders"].Columns["CustID"];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation("CustomersOrders", parentCol, childCol);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}

19. Difference between OLEDB Provider and SqlClient ?
Ans: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.

21. What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database?

    1. System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
    2. System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
    3. System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
    4. System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.

22. Difference between DataReader and DataAdapter / DataSet and DataAdapter?
You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.
After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example.
SqlDataReader myReader = myCommand.ExecuteReader();
You use the Read method of the DataReader object to obtain a row from the results of the query.
while (myReader.Read())
  Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema.
The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.

23. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()

24. Explain different methods and Properties of DataReader which you have used in your project?
Read
GetString
GetInt32
while (myReader.Read())
  Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();

25. What happens when we issue Dataset.ReadXml command?
Reads XML schema and data into the DataSet.

26. In how many ways we can retrieve table records count? How to find the count of records in a dataset?
foreach(DataTable thisTable in myDataSet.Tables){
// For each row, print the values of each column.
foreach(DataRow myRow in thisTable.Rows){

27. How to check if a datareader is closed or opened?
IsClosed()

28. Differences between dataset.clone and dataset.copy?
Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy - Copies both the structure and data for this DataSet.

29. What is method to get XML and schema from Dataset?
ans: getXML () and get Schema ()

 (ASP.NET)

1. Asp.net and asp – differences?

Code Render Block

Code Declaration Block

 

Compiled

Request/Response

Event Driven

 

Object Oriented - Constructors/Destructors, Inheritance, overloading..

 

Exception Handling - Try, Catch, Finally

 

Down-level Support

 

Cultures

 

User Controls

 

In-built client side validation

Session - weren't transferable across servers

It can span across servers, It can survive server crashes, can work with browsers that don't support cookies

built on top of the window & IIS, it was always a separate entity & its functionality was limited.

its an integral part of OS under the .net framework. It shares many of the same objects that traditional applications would use, and all .net objects are available for asp.net's consumption.

 

Garbage Collection

 

Declare variable with datatype

 

In built graphics support

 

Cultures

 

 

 

 

2. Order of events in an asp.net page? Control Execution Lifecycle?

Phase

What a control needs to do

Method or event to override

Initialize

Initialize settings needed during the lifetime of the incoming Web request.

Init event (OnInit method)

Load view state

At the end of this phase, the ViewState property of a control is automatically populated as described in Maintaining State in a Control. A control can override the default implementation of the LoadViewState method to customize state restoration.

LoadViewState method

Process postback data

Process incoming form data and update properties accordingly.

LoadPostData method (if IPostBackDataHandler is implemented)

Load

Perform actions common to all requests, such as setting up a database query. At this point, server controls in the tree are created and initialized, the state is restored, and form controls reflect client-side data.

Load event

(OnLoad method)

Send postback change notifications

Raise change events in response to state changes between the current and previous postbacks.

RaisePostDataChangedEvent method (if IPostBackDataHandler is implemented)

Handle postback events

Handle the client-side event that caused the postback and raise appropriate events on the server.

RaisePostBackEvent method(if IPostBackEventHandler is implemented)

Prerender

Perform any updates before the output is rendered. Any changes made to the state of the control in the prerender phase can be saved, while changes made in the rendering phase are lost.

PreRender event
(OnPreRender method)

Save state

The ViewState property of a control is automatically persisted to a string object after this stage. This string object is sent to the client and back as a hidden variable. For improving efficiency, a control can override the SaveViewState method to modify the ViewState property.

SaveViewState method

Render

Generate output to be rendered to the client.

Render method

Dispose

Perform any final cleanup before the control is torn down. References to expensive resources such as database connections must be released in this phase.

Dispose method

Unload

Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in Dispose and do not handle this event.

UnLoad event (On UnLoad method)

Note   To override an EventName event, override the OnEventName method (and call base. OnEventName).

(Session/State)

3. Application and Session Events
The ASP.NET page framework provides ways for you to work with events that can be raised when your application starts or stops or when an individual user's session starts or stops:

    1. Application events are raised for all requests to an application. For example, Application_BeginRequest is raised when any Web Forms page or XML Web service in your application is requested. This event allows you to initialize resources that will be used for each request to the application. A corresponding event, Application_EndRequest, provides you with an opportunity to close or otherwise dispose of resources used for the request.
    2. Session events are similar to application events (there is a Session_OnStart and a Session_OnEnd event), but are raised with each unique session within the application. A session begins when a user requests a page for the first time from your application and ends either when your application explicitly closes the session or when the session times out.

You can create handlers for these types of events in the Global.asax file.

4. Difference between ASP Session and ASP.NET Session?
asp.net session supports cookie less session & it can span across multiple servers.

5. What is cookie less session? How it works?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. If cookies are not available, a session can be tracked by adding a session identifier to the URL. This can be enabled by setting the following:
<sessionState cookieless="true" />
6. handling in a webfarm, how does it work and what are the limits?
By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. Additionally, ASP.NET can store session data in an external process, which can even reside on another machine. To enable this feature:

  • Start the ASP.NET state service, either using the Services snap-in or by executing "net start aspnet_state" on the command line. The state service will by default listen on port 42424. To change the port, modify the registry key for the service: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\Port
  • Set the mode attribute of the <sessionState> section to "StateServer".
  • Configure the stateConnectionString attribute with the values of the machine on which you started aspnet_state.

The following sample assumes that the state service is running on the same machine as the Web server ("localhost") and uses the default port (42424):

<sessionState
                mode="StateServer"
                stateConnectionString="tcpip=localhost:42424"
              />

Note that if you try the sample above with this setting, you can reset the Web server (enter iisreset on the command line) and the session state value will persist. **

7. What method do you use to explicitly kill a users session?
Abandon()

8. What are the different ways you would consider sending data across pages in ASP (i.e between 1.asp to 2.asp)?
Session
public properties

9. What is State Management in .Net and how many ways are there to maintain a state in .Net? What is view state?
Web pages are recreated each time the page is posted to the server. In traditional Web programming, this would ordinarily mean that all information associated with the page and the controls on the page would be lost with each round trip.
To overcome this inherent limitation of traditional Web programming, the ASP.NET page framework includes various options to help you preserve changes — that is, for managing state. The page framework includes a facility called view state that automatically preserves property values of the page and all the controls on it between round trips.
However, you will probably also have application-specific values that you want to preserve. To do so, you can use one of the state management options.
Client-Based State Management Options:
View State
Hidden Form Fields
Cookies
Query Strings
Server-Based State Management Options
Application State
Session State
Database Support

10. What are the disadvantages of view state / what are the benefits?
Automatic view-state management is a feature of server controls that enables them to repopulate their property values on a round trip (without you having to write any code). This feature does impact performance, however, since a server control's view state is passed to and from the server in a hidden form field. You should be aware of when view state helps you and when it hinders your page's performance.

11. When maintaining session through Sql server, what is the impact of Read and Write operation on Session objects? will performance degrade?
Maintaining state using database technology is a common practice when storing user-specific information where the information store is large. Database storage is particularly useful for maintaining long-term state or state that must be preserved even if the server must be restarted.
 

12. Explain the differences between Server-side and Client-side code?
Server side code will process at server side & it will send the result to client. Client side code (javascript) will execute only at client side.

13. Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting platform?
A:  Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the shared hosting platform.  Certain options can affect the security, performance and stability of the server and, therefore cannot be changed.  The following settings are the only ones that can be changed in your site's web.config file (s):
browserCaps
clientTarget
pages
customErrors
globalization
authorization
authentication
webControls
webServices
 

14. What is Role-Based security?
A role is a named set of principals that have the same privileges with respect to security (such as a teller or a manager). A principal can be a member of one or more roles. Therefore, applications can use role membership to determine whether a principal is authorized to perform a requested action.

15. What are the different authentication modes in the .NET environment?

<authentication mode="Windows|Forms|Passport|None">
   <forms name="name"
                      loginUrl="url" 
                      protection="All|None|Encryption|Validation"
                      timeout="30" path="/" >
                      requireSSL="true|false"
                      slidingExpiration="true|false">
      <credentials passwordFormat="Clear|SHA1|MD5">
         <user name="username" password="password"/>
      </credentials>
                 </forms>
   <passport redirectUrl="internal"/>
</authentication>

Attribute

Option

Description

mode

   

Controls the default authentication mode for an application.

   

Windows

Specifies Windows authentication as the default authentication mode. Use this mode when using any form of Microsoft Internet Information Services (IIS) authentication: Basic, Digest, Integrated Windows authentication (NTLM/Kerberos), or certificates.

   

Forms

Specifies ASP.NET forms-based authentication as the default authentication mode.

   

Passport

Specifies Microsoft Passport authentication as the default authentication mode.

   

None

Specifies no authentication. Only anonymous users are expected or applications can handle events to provide their own authentication.

16. How do you specify whether your data should be passed as Query string and Forms (Mainly about POST and GET)
Through attribute tag of form tag.

17. What are validator? Name the Validation controls in asp.net? How do u disable them? Will the asp.net validators run in server side or client side? How do you do Client-side validation in .Net? How to disable validator control by client side JavaScript?
A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation ("EnableClientScript" property set to true/false) using client script.
The following validation controls are available in asp.net:
RequiredFieldValidator Control, CompareValidator Control, RangeValidator Control, RegularExpressionValidator Control, CustomValidator Control, ValidationSummary Control.

 

18. Which two properties are there on every validation control?
ControlToValidate, ErrorMessage

19. How do you use css in asp.net?
Within the <HEAD> section of an HTML document that will use these styles, add a link to this external CSS style sheet that
follows this form:
<LINK REL="STYLESHEET" TYPE="text/css" HREF="MyStyles.css">
MyStyles.css is the name of your external CSS style sheet.

20. How do you implement postback with a text box? What is postback and usestate?
Make AutoPostBack property to true

21. What is SQL injection?
An SQL injection attack "injects" or manipulates SQL code by adding unexpected SQL to a query.
Many web pages take parameters from web user, and make SQL query to the database. Take for instance when a user login, web page that user name and password and make SQL query to the database to check if a user has valid name and password.
Username: ' or 1=1 ---
Password: [Empty]
This would execute the following query against the users table:
select count(*) from users where userName='' or 1=1 --' and userPass=''

22. Asp.net - How to find last error which occurred?
A: Server.GetLastError();
[C#]
Exception LastError;
String ErrMessage;
LastError = Server.GetLastError();
if (LastError != null)
ErrMessage = LastError.Message;
else
ErrMessage = "No Errors";
Response.Write("Last Error = " + ErrMessage);

23. How to do Caching in ASP?
A: <%@ OutputCache Duration="60" VaryByParam="None" %>

VaryByParam value

Description

none

One version of page cached (only raw GET)

*

n versions of page cached based on query string and/or POST body

v1

n versions of page cached based on value of v1 variable in query string or POST body

v1;v2

n versions of page cached based on value of v1 and v2 variables in query string or POST body

<%@ OutputCache Duration="60" VaryByParam="none" %>
<%@ OutputCache Duration="60" VaryByParam="*" %>
<%@ OutputCache Duration="60" VaryByParam="name;age" %>
The OutputCache directive supports several other cache varying options

1.    VaryByHeader - maintain separate cache entry for header string changes (UserAgent, UserLanguage, etc.)

2.    VaryByControl - for user controls, maintain separate cache entry for properties of a user control

3.    VaryByCustom - can specify separate cache entries for browser types and version or provide a custom GetVaryByCustomString method in HttpApplicationderived class

24. What is the Global ASA(X) File?

25. Any alternative to avoid name collisions other then Namespaces.
A scenrio that two namespaces named N1 and N2 are there both having the same class say A. now in another class i ve written
using N1;using N2;
and i am instantiating class A in this class. Then how will u avoid name collisions?
Ans: using alias
Eg: using MyAlias = MyCompany.Proj.Nested;

Can you edit data in the Repeater control? Which template must you provide, in order to display data in a Repeater control? How can you provide an alternating color scheme in a Repeater control? What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?

26. What is the use of web.config? Difference between machine.config and Web.config?
ASP.NET configuration files are XML-based text files--each named web.config--that can appear in any directory on an ASP.NET Web application server. Each web.config file applies configuration settings to the directory it is located in and to all virtual child directories beneath it. Settings in child directories can optionally override or modify settings specified in parent directories. The root configuration file--WinNT\Microsoft.NET\Framework\<version>\config\machine.config--provides
default configuration settings for the entire machine. ASP.NET configures IIS to prevent direct browser access to web.config files to ensure that their values cannot become public (attempts to access them will cause ASP.NET to return 403: Access Forbidden). At run time ASP.NET uses these web.config configuration files to hierarchically compute a unique collection of settings for each incoming URL target request (these settings are calculated only once and then cached across subsequent requests; ASP.NET automatically watches for file changes and will invalidate the cache if any of the configuration files change).
27. What is the use of sessionstate tag in the web.config file?
Configuring session state:
Session state features can be configured via the <sessionState> section in a web.config file. To double the default timeout of 20 minutes, you can add the following to the web.config file of an application:
<sessionState
timeout="40"
/>

28. What are the different modes for the sessionstates in the web.config file?

Off

Indicates that session state is not enabled.

Inproc

Indicates that session state is stored locally.

StateServer

Indicates that session state is stored on a remote server.

SQLServer

Indicates that session state is stored on the SQL Server.

29. What is smart navigation?
When a page is requested by an Internet Explorer 5 browser, or later, smart navigation enhances the user's experience of the page by performing the following:

1.    eliminating the flash caused by navigation.

2.    persisting the scroll position when moving from page to page.

3.    persisting element focus between navigations.

4.    retaining only the last page state in the browser's history.

Smart navigation is best used with ASP.NET pages that require frequent postbacks but with visual content that does not change dramatically on return. Consider this carefully when deciding whether to set this property to true.
Set the SmartNavigation attribute to true in the @ Page directive in the .aspx file. When the page is requested, the dynamically generated class sets this property.

30. What base class do all Web Forms inherit from?
System.Web.UI.Page

31. Is it possible for me to change my aspx file extension to some other name?
Yes.
Open IIS->Default Website -> Properties
Select HomeDirectory tab
Click on configuration button
Click on add. Enter aspnet_isapi details (C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\aspnet_isapi.dll   |  GET,HEAD,POST,DEBUG)

Open machine.config(C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\CONFIG) & add new extension under <httpHandlers> tag
<add verb="*" path="*.santhosh" type="System.Web.UI.PageHandlerFactory"/>

 (WEBSERVICE & REMOTING)

1. What is a WebService and what is the underlying protocol used in it? Namespace?
Web Services are applications delivered as a service on the Web. Web services allow for programmatic access of business logic over the Web. Web services typically rely on XML-based protocols, messages, and interface descriptions for communication and access. Web services are designed to be used by other programs or applications rather than directly by end user. Programs invoking a Web service are called clients. SOAP over HTTP is the most commonly used protocol for invoking Web services.

2. Why Web Services?
By exposing data and functionality using standard protocols, Web services make it easy to build sophisticated applications that integrate many features and content. There are three main uses of Web services. Application integration Web services within an intranet are commonly used to integrate business applications running on disparate platforms. For example, a .NET client running on Windows 2000 can easily invoke a Java Web service running on a mainframe or Unix machine to retrieve data from a legacy application. Business integration Web services allow trading partners to engage in e-business leveraging the existing Internet infrastructure. Organizations can send electronic purchase orders to suppliers and receive electronic invoices. Doing e-business with Web services means a low barrier to entry because Web services can be added to existing applications running on any platform without changing legacy code. Commercial Web services focus on selling content and business services to clients over the Internet similar to familiar Web pages. Unlike Web pages, commercial Web services target applications not humans as their direct users. Continental Airlines exposes flight schedules and status Web services for travel Web sites and agencies to use in their applications. Like Web pages, commercial Web services are valuable only if they expose a valuable service or content. It would be very difficult to get customers to pay you for using a Web service that creates business charts with the customers? data. Customers would rather buy a charting component (e.g. COM or .NET component) and install it on the same machine as their application. On the other hand, it makes sense to sell real-time weather information or stock quotes as a Web service. Technology can help you add value to your services and explore new markets, but ultimately customers pay for contents and/or business services, not for technology

3. In a Webservice, need to display 10 rows from a table. So DataReader or DataSet is best choice?
A: WebService will support only DataSet.

4. Are Web Services a replacement for other distributed computing platforms?
No. Web Services is just a new way of looking at existing implementation platforms.

5. What is SOAP, WSDL, UDDI and the concept behind Web Services? What are various components of WSDL? What is the use of WSDL.exe utility?
SOAP is an XML-based messaging framework specifically designed for exchanging formatted data across the Internet, for example using request and reply messages or sending entire documents. SOAP is simple, easy to use, and completely neutral with respect to operating system, programming language, or distributed computing platform.
After SOAP became available as a mechanism for exchanging XML messages among enterprises (or among disparate applications within the same enterprise), a better way was needed to describe the messages and how they are exchanged. The Web Services Description Language (WSDL) is a particular form of an XML Schema, developed by Microsoft and IBM for the purpose of defining the XML message, operation, and protocol mapping of a web service accessed using SOAP or other XML protocol. WSDL defines web services in terms of "endpoints" that operate on XML messages. The WSDL syntax allows both the messages and the operations on the messages to be defined abstractly, so they can be mapped to multiple physical implementations. The current WSDL spec describes how to map messages and operations to SOAP 1.1, HTTP GET/POST, and MIME. WSDL creates web service definitions by mapping a group of endpoints into a logical sequence of operations on XML messages. The same XML message can be mapped to multiple operations (or services) and bound to one or more communications protocols (using "ports").
The Universal Description, Discovery, and Integration (UDDI) framework defines a data model (in XML) and SOAP APIs for registration and searches on business information, including the web services a business exposes to the Internet. UDDI is an independent consortium of vendors, founded by Microsoft, IBM, and Ariba, for the purpose of developing an Internet standard for web service description registration and discovery. Microsoft, IBM, and Ariba also are hosting the initial deployment of a UDDI service, which is conceptually patterned after DNS (the Internet service that translates URLs into TCP addresses). UDDI uses a private agreement profile of SOAP (i.e. UDDI doesn't use the SOAP serialization format because it's not well suited to passing complete XML documents (it's aimed at RPC style interactions). The main idea is that businesses use the SOAP APIs to register themselves with UDDI, and other businesses search UDDI when they want to discover a trading partner, for example someone from whom they wish to procure sheet metal, bolts, or transistors. The information in UDDI is categorized according to industry type and geographical location, allowing UDDI consumers to search through lists of potentially matching businesses to find the specific one they want to contact. Once a specific business is chosen, another call to UDDI is made to obtain the specific contact information for that business. The contact information includes a pointer to the target business's WSDL or other XML schema file describing the web service that the target business publishes.

6. How to generate proxy class other than .net app and wsdl tool?
To access an XML Web service from a client application, you first add a Web reference, which is a reference to an XML Web service. When you create a Web reference, Visual Studio creates an XML Web service proxy class automatically and adds it to your project. This proxy class exposes the methods of the XML Web service and handles the marshalling of appropriate arguments back and forth between the XML Web service and your application. Visual Studio uses the Web Services Description Language (WSDL) to create the proxy.
To generate an XML Web service proxy class:

    1. From a command prompt, use Wsdl.exe to create a proxy class, specifying (at a minimum) the URL to an XML Web service or a service description, or the path to a saved service description.
      Wsdl /language:language  /protocol:protocol /namespace:myNameSpace /out:filename
      /username:username /password:password /domain:domain <url or path>

7. What is a proxy in web service? How do I use a proxy server when invoking a Web service?
If you are using the SOAP Toolkit, you need to set some connector properties to use a proxy server: Dim soap As SoapClient Set soap=New SoapClient soap.ConnectorProperty("ProxyServer") = ?proxyservername? soap.ConnectorProperty("ProxyPort") = ?8080? soap.ConnectorProperty("UseProxy") = True While with .NET , you just need to create a System.Net.WebProxy object and use it to set the Proxy property Dim webs As localhost.MyService() webs.Proxy=New System.Net.WebProxy(?http://proxyserver:8080?)

8. How you will protect / secure a web service?
For the most part, things that you do to secure a Web site can be used to secure a Web Service. If you need to encrypt the data exchange, you use Secure Sockets Layer (SSL) or a Virtual Private Network to keep the bits secure. For authentication, use HTTP Basic or Digest authentication with Microsoft® Windows® integration to figure out who the caller is.
these items cannot:

    1. Parse a SOAP request for valid values
    2. Authenticate access at the Web Method level (they can authenticate at the Web Service level)
    3. Stop reading a request as soon as it is recognized as invalid

9. What is Remoting?
The process of communication between different operating system processes, regardless of whether they are on the same computer. The .NET remoting system is an architecture designed to simplify communication between objects living in different application domains, whether on the same computer or not, and between different contexts, whether in the same application domain or not.

10. Difference between web services & remoting?   (IMP)

 

ASP.NET Web Services

.NET Remoting

Protocol

Can be accessed only over HTTP

Can be accessed over any protocol (including TCP, HTTP, SMTP and so on)

State Management

Web services work in a stateless environment

Provide support for both stateful and stateless environments through Singleton and SingleCall objects

Type System

Web services support only the datatypes defined in the XSD type system, limiting the number of objects that can be serialized.

Using binary communication, .NET Remoting can provide support for rich type system

Interoperability

Web services support interoperability across platforms, and are ideal for heterogeneous environments.

.NET remoting requires the client be built using .NET, enforcing homogenous environment.

Reliability

Highly reliable due to the fact that Web services are always hosted in IIS

Can also take advantage of IIS for fault isolation. If IIS is not used, application needs to provide plumbing for ensuring the reliability of the application.

Extensibility

Provides extensibility by allowing us to intercept the SOAP messages during the serialization and deserialization stages.

Very extensible by allowing us to customize the different components of the .NET remoting framework.

Ease-of-Programming

Easy-to-create and deploy.

Complex to program.

Though both the .NET Remoting infrastructure and ASP.NET Web services can enable cross-process communication, each is designed to benefit a different target audience. ASP.NET Web services provide a simple programming model and a wide reach. .NET Remoting provides a more complex programming model and has a much narrower reach.
As explained before, the clear performance advantage provided by TCPChannel-remoting should make you think about using this channel whenever you can afford to do so. If you can create direct TCP connections from your clients to your server and if you need to support only the .NET platform, you should go for this channel. If you are going to go cross-platform or you have the requirement of supporting SOAP via HTTP, you should definitely go for ASP.NET Web services.
Both the .NET remoting and ASP.NET Web services are powerful technologies that provide a suitable framework for developing distributed applications. It is important to understand how both technologies work and then choose the one that is right for your application. For applications that require interoperability and must function over public networks, Web services are probably the best bet. For those that require communications with other .NET components and where performance is a key priority, .NET Remoting is the best choice. In short, use Web services when you need to send and receive data from different computing platforms, use .NET Remoting when sending and receiving data between .NET applications. In some architectural scenarios, you might also be able to use.NET Remoting in conjunction with ASP.NET Web services and take advantage of the best of both worlds.
The Key difference between ASP.NET webservices and .NET Remoting is how they serialize data into messages and the format they choose for metadata.  ASP.NET uses XML serializer for serializing or Marshalling. And XSD is used for Metadata.  .NET Remoting relies on
System.Runtime.Serialization.Formatter.Binary and System.Runtime.Serialization.SOAPFormatter and relies on .NET CLR Runtime assemblies for metadata.

11. CAO and SAO.
Client Activated objects are those remote objects whose Lifetime is directly Controlled by the client. This is in direct contrast to SAO. Where the server, not the client has complete control over the lifetime of the objects.
Client activated objects are instantiated on the server as soon as the client request the object to be created. Unlike as SAO a CAO doesn't delay the object creation until the first method is called on the object. (In SAO the object is instantiated when the client calls the method on the object)

12. singleton and singlecall.
Singleton
types never have more than one instance at any one time. If an instance exists, all client requests are serviced by that instance.
Single Call types always have one instance per client request. The next method invocation will be serviced by a different server instance, even if the previous instance has not yet been recycled by the system.

 (XML)

1. Explain what a DiffGram is, and a good use for one?
A DiffGram is an XML format that is used to identify current and original versions of data elements. When sending and retrieving a DataSet from an XML Web service, the DiffGram format is implicitly used.
The DataSet uses the DiffGram format to load and persist its contents, and to serialize its contents for transport across a network connection. When a DataSet is written as a DiffGram, it populates the DiffGram with all the necessary information to accurately recreate the contents, though not the schema, of the DataSet, including column values from both the Original and Current row versions, row error information, and row order.
DiffGram Format
The DiffGram format is divided into three sections: the current data, the original (or "before") data, and an errors section, as shown in the following example.

<?xml version="1.0"?>
                            <diffgr:diffgram
                                     xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
                                     xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1"
                                     xmlns:xsd="http://www.w3.org/2001/XMLSchema">
 
                               <DataInstance>
                               </DataInstance>
 
                              <diffgr:before>
                              </diffgr:before>
 
                              <diffgr:errors>
                              </diffgr:errors>
</diffgr:diffgram>

The DiffGram format consists of the following blocks of data:

<DataInstance>

The name of this element, DataInstance, is used for explanation purposes in this documentation. A DataInstance element represents a DataSet or a row of a DataTable. Instead of DataInstance, the element would contain the name of the DataSet or DataTable. This block of the DiffGram format contains the current data, whether it has been modified or not. An element, or row, that has been modified is identified with the diffgr:hasChanges annotation.

<diffgr:before>

This block of the DiffGram format contains the original version of a row. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation.

<diffgr:errors>

This block of the DiffGram format contains error information for a particular row in the DataInstance block. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation.

2. Write syntax to serialize class using XML Serializer?

(IIS)

1. In which process does IIS runs (was asking about the EXE file)
inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things.  When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.

2. Where are the IIS log files stored?
C:\WINDOWS\system32\Logfiles\W3SVC1
    OR
c:\winnt\system32\LogFiles\W3SVC1

3. What are the different IIS authentication modes in IIS 5.0 and Explain? Difference between basic and digest authentication modes?
IIS provides a variety of authentication schemes:

1.    Anonymous (enabled by default)

2.    Basic

3.    Digest

4.    Integrated Windows authentication (enabled by default)

5.    Client Certificate Mapping

Anonymous
Anonymous authentication gives users access to the public areas of your Web site without prompting them for a user name or password. Although listed as an authentication scheme, it is not technically performing any client authentication because the client is not required to supply any credentials. Instead, IIS provides stored credentials to Windows using a special user account, IUSR_machinename. By default, IIS controls the password for this account. Whether or not IIS controls the password affects the permissions the anonymous user has. When IIS controls the password, a sub authentication DLL (iissuba.dll) authenticates the user using a network logon. The function of this DLL is to validate the password supplied by IIS and to inform Windows that the password is valid, thereby authenticating the client. However, it does not actually provide a password to Windows. When IIS does not control the password, IIS calls the LogonUser() API in Windows and provides the account name, password and domain name to log on the user using a local logon. After the logon, IIS caches the security token and impersonates the account. A local logon makes it possible for the anonymous user to access network resources, whereas a network logon does not.
Basic Authentication

IIS Basic authentication as an implementation of the basic authentication scheme found in section 11 of the HTTP 1.0 specification.
As the specification makes clear, this method is, in and of itself, non-secure. The reason is that Basic authentication assumes a trusted connection between client and server. Thus, the username and password are transmitted in clear text. More specifically, they are transmitted using Base64 encoding, which is trivially easy to decode. This makes Basic authentication the wrong choice to use over a public network on its own.
Basic Authentication is a long-standing standard supported by nearly all browsers. It also imposes no special requirements on the server side -- users can authenticate against any NT domain, or even against accounts on the local machine. With SSL to shelter the security credentials while they are in transmission, you have an authentication solution that is both highly secure and quite flexible.
Digest Authentication
The Digest authentication option was added in Windows 2000 and IIS 5.0. Like Basic authentication, this is an implementation of a technique suggested by Web standards, namely RFC 2069 (superceded by RFC 2617).
Digest authentication also uses a challenge/response model, but it is much more secure than Basic authentication (when used without SSL). It achieves this greater security not by encrypting the secret (the password) before sending it, but rather by following a different design pattern -- one that does not require the client to transmit the password over the wire at all.
Instead of sending the password itself, the client transmits a one-way message digest (a checksum) of the user's password, using (by default) the MD5 algorithm. The server then fetches the password for that user from a Windows 2000 Domain Controller, reruns the checksum algorithm on it, and compares the two digests. If they match, the server knows that the client knows the correct password, even though the password itself was never sent. (If you have ever wondered what the default ISAPI filter "md5filt" that is installed with IIS 5.0 is used for, now you know.
Integrated Windows Authentication
Integrated Windows authentication (formerly known as NTLM authentication and Windows NT Challenge/Response authentication) can use either NTLM or Kerberos V5 authentication and only works with Internet Explorer 2.0 and later.
When Internet Explorer attempts to access a protected resource, IIS sends two WWW-Authenticate headers, Negotiate and NTLM.

1.    If Internet Explorer recognizes the Negotiate header, it will choose it because it is listed first. When using Negotiate, the browser will return information for both NTLM and Kerberos. At the server, IIS will use Kerberos if both the client (Internet Explorer 5.0 and later) and server (IIS 5.0 and later) are running Windows 2000 and later, and both are members of the same domain or trusted domains. Otherwise, the server will default to using NTLM.

2.    If Internet Explorer does not understand Negotiate, it will use NTLM.

So, which mechanism is used depends upon a negotiation between Internet Explorer and IIS.
When used in conjunction with Kerberos v5 authentication, IIS can delegate security credentials among computers running Windows 2000 and later that are trusted and configured for delegation. Delegation enables remote access of resources on behalf of the delegated user.
Integrated Windows authentication is the best authentication scheme in an intranet environment where users have Windows domain accounts, especially when using Kerberos. Integrated Windows authentication, like digest authentication, does not pass the user's password across the network. Instead, a hashed value is exchanged.
Client Certificate Mapping
A certificate is a digitally signed statement that contains information about an entity and the entity's public key, thus binding these two pieces of information together. A trusted organization (or entity) called a Certification Authority (CA) issues a certificate after the CA verifies that the entity is who it says it is. Certificates can contain different types of data. For example, an X.509 certificate includes the format of the certificate, the serial number of the certificate, the algorithm used to sign the certificate, the name of the CA that issued the certificate, the name and public key of the entity requesting the certificate, and the CA's signature. X.509 client certificates simplify authentication for larger user bases because they do not rely on a centralized account database. You can verify a certificate simply by examining the certificate.

 

3. IIS Isolation Levels?
Internet Information Server introduced the notion "Isolation Level", which is also present in IIS4 under a different name. IIS5 supports three isolation levels, that you can set from the Home Directory tab of the site's Properties dialog:

  • Low (IIS Process): ASP pages run in INetInfo.Exe, the main IIS process, therefore they are executed in-process. This is the fastest setting, and is the default under IIS4. The problem is that if ASP crashes, IIS crashes as well and must be restarted (IIS5 has a reliable restart feature that automatically restarts a server when a fatal error occurs).
  • Medium (Pooled): In this case ASP runs in a different process, which makes this setting more reliable: if ASP crashes IIS won't. All the ASP applications at the Medium isolation level share the same process, so you can have a web site running with just two processes (IIS and ASP process). IIS5 is the first Internet Information Server version that supports this setting, which is also the default setting when you create an IIS5 application. Note that an ASP application that runs at this level is run under COM+, so it's hosted in DLLHOST.EXE (and you can see this executable in the Task Manager).
  • High (Isolated): Each ASP application runs out-process in its own process space, therefore if an ASP application crashes, neither IIS nor any other ASP application will be affected. The downside is that you consume more memory and resources if the server hosts many ASP applications. Both IIS4 and IIS5 supports this setting: under IIS4 this process runs inside MTS.EXE, while under IIS5 it runs inside DLLHOST.EXE.

When selecting an isolation level for your ASP application, keep in mind that out-process settings - that is, Medium and High - are less efficient than in-process (Low). However, out-process communication has been vastly improved under IIS5, and in fact IIS5's Medium isolation level often deliver better results than IIS4's Low isolation. In practice, you shouldn't set the Low isolation level for an IIS5 application unless you really need to serve hundreds pages per second.

Controls

4. How do I upload a file from my ASP.NET page?
A: In order to perform file upload in your ASP.NET page, you will need to use two classes: the System.Web.UI.HtmlControls.HtmlInputFile class and the System.Web.HttpPostedFile class. The HtmlInputFile class represents and HTML input control that the user will use on the client side to select a file to upload. The HttpPostedFile class represents the uploaded file and is obtained from the PostedFile property of the HtmlInputFile class. In order to use the HtmlInputFile control, you need to add the enctype attribute to your form tag as follows:
<form id="upload" method="post" runat="server" enctype="multipart/form-data">
Also, remember that the /data directory is the only directory with Write permissions enabled for the anonymous user. Therefore, you will need to make sure that the your code uploads the file to the /data directory or one of its subdirectories.
Below is a simple example of how to upload a file via an ASP.NET page in C# and VB.NET.
C#
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.UI.HtmlControls" %>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Drawing" %>
<html>
<head>
<title>upload_cs</title>
</head>
<script language="C#" runat="server">
public void UploadFile(object sender, EventArgs e)
{
if (loFile.PostedFile != null)
{
try
{
string strFileName, strFileNamePath, strFileFolder;
strFileFolder = Context.Server.MapPath(@"data\");
strFileName = loFile.PostedFile.FileName;
strFileName = Path.GetFileName(strFileName);
strFileNamePath = strFileFolder + strFileName;
loFile.PostedFile.SaveAs(strFileNamePath);
lblFileName.Text = strFileName;
lblFileLength.Text = loFile.PostedFile.ContentLength.ToString();
lblFileType.Text = loFile.PostedFile.ContentType;
pnStatus.Visible = true;
}
catch (Exception x)
{
Label lblError = new Label();
lblError.ForeColor = Color.Red;
lblError.Text = "Exception occurred: " + x.Message;
lblError.Visible = true;
this.Controls.Add(lblError);
}
}
}
</script>
<body>
<form id="upload_cs" method="post" runat="server" enctype="multipart/form-data">
<P>
<INPUT type="file" id="loFile" runat="server">
</P>
<P>
<asp:Button id="btnUpload" runat="server" Text=" Upload " OnClick="UploadFile"></asp:Button></P>
<P>
<asp:Panel id="pnStatus" runat="server" Visible="False">
<asp:Label id="lblFileName" Font-Bold="True" Runat="server"></asp:Label> uploaded<BR>
<asp:Label id="lblFileLength" Runat="server"></asp:Label> bytes<BR>
<asp:Label id="lblFileType" Runat="server"></asp:Label>
</asp:Panel></P>
</form>
</body>
</html>

5. How do I send an email message from my ASP.NET page?
A: You can use the System.Web.Mail.MailMessage and the System.Web.Mail.SmtpMail class to send email in your ASPX pages. Below is a simple example of using this class to send mail in C# and VB.NET. In order to send mail through our mail server, you would want to make sure to set the static SmtpServer property of the SmtpMail class to mail-fwd.
C#
<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Web" %>
<%@ Import Namespace="System.Web.Mail" %>
<HTML>
<HEAD>
<title>Mail Test</title>
</HEAD>
<script language="C#" runat="server">
private void Page_Load(Object sender, EventArgs e)
{
try
{
MailMessage mailObj = new MailMessage();
mailObj.From = "sales@joeswidgets.com";
mailObj.To = "ringleader@forexample-domain.com";
mailObj.Subject = "Your Widget Order";
mailObj.Body = "Your order was processed.";
mailObj.BodyFormat = MailFormat.Text;
SmtpMail.SmtpServer = "mail-fwd";
SmtpMail.Send(mailObj);
Response.Write("Mail sent successfully");
}
catch (Exception x)
{
Response.Write("Your message was not sent: " + x.Message);
}
}
</script>
<body>
<form id="mail_test" method="post" runat="server">
</form>
</body>
</HTML>

 

6. What is reflection?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember ) ,  or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).

 

7. What is the difference between Finalize and Dispose (Garbage collection) ?

Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object. In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object.

Dispose can be called even if other references to the object are alive. Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from

permanently leaking if the programmer fails to call Dispose.

 

 

8. Changes to which portion of version number indicates an incompatible change?
Major or minor. Changes to the major or minor portion of the version number indicate an incompatible change. Under this convention then, version 2.0.0.0 would be considered incompatible with version 1.0.0.0. Examples of an incompatible change would be a change to the types of some method parameters or the removal of a type or method altogether. Build. The Build number is typically used to distinguish between daily builds or smaller compatible releases. Revision. Changes to the revision number are typically reserved for an incremental build needed to fix a particular bug. You'll sometimes hear this referred to as the "emergency bug fix" number in that the revision is what is often changed when a fix to a specific bug is shipped to a customer.

9. What is side-by-side execution? Can two application one using private assembly and other using Shared assembly be stated as a side-by-side executables?
Side-by-side execution is the ability to run multiple versions of an application or component on the same computer. You can have multiple versions of the common language runtime, and multiple versions of applications and components that use a version of the runtime, on the same computer at the same time. Since versioning is only applied to shared assemblies, and not to private assemblies, two application one using private assembly and one using shared assembly cannot be stated as side-by-side

executables.

 

Why string are called Immutable data Type ?
10.
The memory representation of string is an Array of Characters, So on re-assigning the new array of Char is formed & the start address is changed . Thus keeping the Old string in Memory for Garbage Collector to be disposed.

 

11. What does assert() method do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

 

12. What's the difference between the Debug class and Trace class?
Documentation looks the same.  Use Debug class for debug builds, use Trace class for both debug and release builds.

 

13. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose.  For applications that are constantly running you run the risk of overloading the machine and the hard drive.  Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.

 

14. Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.

 

15. How do assemblies find each other?
By searching directory paths. There are several factors which can affect the path (such as the AppDomain host, and application configuration files), but for private assemblies the search path is normally the application's directory and its sub-directories. For shared assemblies, the search path is normally same as the private assembly path plus the shared assembly cache.

 

16. How does assembly versioning work?
Each assembly has a version number called the compatibility version. Also each reference to an assembly (from another assembly) includes both the name and version of the referenced assembly.The version number has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the first two parts different are normally viewed as incompatible. If the first two parts are the same, but the third is different, the assemblies are deemed as 'maybe compatible'. If only the fourth part is different, the assemblies are deemed compatible. However, this is just the default guideline - it is the version policy that decides to what extent these rules are enforced. The version policy can be specified via the application configuration file.

 

17. What is garbage collection?
Garbage collection is a system whereby a run-time component takes responsibility for managing the lifetime of objects and the heap memory that they occupy. This concept is not new to .NET - Java and many other languages/runtimes have used garbage collection for some time.

 

18. Why doesn't the .NET runtime offer deterministic destruction?
Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn't find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn't get notified immediately when the final reference on an object goes away - it only finds out during the next sweep of the heap.
Futhermore, this type of algorithm works best by performing the garbage collection sweep as rarely as possible. Normally heap exhaustion is the trigger for a collection sweep.

 

19. Is the lack of deterministic destruction in .NET a problem?
It's certainly an issue that affects component design. If you have objects that maintain expensive or scarce resources (e.g. database locks), you need to provide some way for the client to tell the object to release the resource when it is done. Microsoft recommend that you provide a method called Dispose() for this purpose. However, this causes problems for distributed objects - in a distributed system who calls the Dispose() method? Some form of reference-counting or ownership-management mechanism is needed to handle distributed objects - unfortunately the runtime offers no help with this.

 

20. What is serialization?
Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization / Deserialization is mostly used to transport objects (e.g. during remoting), or to persist

objects (e.g. to a file or database).

 

21. Does the .NET Framework have in-built support for serialization?
There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.

 

22. Can I customise the serialization process?
Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement]

attribute, which can be used to specify the XML element name to be used for a particular property or field.
Serialization via SoapFormatter/BinaryFormatter can also be controlled to some extent by attributes. For example, the [NonSerialized] attribute is the equivalent of XmlSerializer's [XmlIgnore] attribute. Ultimate control of the serialization process can be acheived by implementing the the ISerializable interface on the class whose instances are to be serialized.

 

23. Why is XmlSerializer so slow?
There is a once-per-process-per-type overhead with XmlSerializer. So the first time you serialize or deserialize an object of a given type in an application, there is a significant delay. This normally doesn't matter, but it may mean, for example, that XmlSerializer is a poor choice for loading configuration settings during startup of a GUI application.

 

24. Why do I get errors when I try to serialize a Hashtable?
XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

 

25. What are attributes?
There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection.
The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context attributes provide an interception mechanism whereby instance activation and method calls can be

pre- and/or post-processed.

26. What is Boxing and unboxing ?
Boxing:
The conversion of a value type instance to an object, which implies that the instance will carry full type information at run time and will be allocated in the heap. The Microsoft intermediate language (MSIL) instruction set's box instruction converts a value type to an object by making a copy of the value type and embedding it in a newly allocated object.

 

Un-Boxing:
The conversion of an object instance to a value type.

 

27.How do you enforce garbage collection in .NET?
System.GC.Collect();

28. How's method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the  same name within the class.

 

29. What does the keyword virtual mean in the method definition?
The method can be over-ridden.

30.What's the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

 

31. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.

 

32. Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.

 

33. What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.


34. What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception  test

cases (exceptions are thrown and caught properly).

 

35. Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

 

36. What's the implicit name of the parameter that gets passed into the class' set method?
Value, and it's datatype depends on whatever variable we're changing.

 

37. How do you inherit from a class in C#?
Place a colon and then the name of the base class. Notice that it's double colon in C++.

 

38. Does C# support multiple inheritance?
No, use interfaces instead.

 

39. When you inherit a protected class-level variable, who is it available to?
Derived Classes.

 

40. What's the top .NET class that everything is derived from?
System.Object.

 

41. Can you declare the override method static while the original method is non-static?
No, you can't, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword  override.

 

42. Can you override private virtual methods?
No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

 

 

 

43. Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that's what keyword sealed in the class definition is for. The developer trying to derive from your class will get a  message: cannot inherit from Sealed class WhateverBaseClassName. It's the same concept as final class in Java.

 

44. Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.

 

45. Why can't you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it's public by default.

 

46. Can you inherit multiple interfaces?
Yes, why not.

 

47. And if they have conflicting method names?
It's up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you're

okay.

 

48. What's the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

 

49. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.

 

50. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

 

52. What's the difference between System.String and System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

 

53. Does C# support multiple-inheritance?
No, use interfaces instead.

 

54. When you inherit a protected class-level variable, who is it available to?
The derived class.

 

55. Are private class-level variables inherited?
Yes, but they are not accessible.  Although they are not visible or accessible via the class interface, they are inherited.

 

56. Describe the accessibility modifier "protected internal".
It is available to derived classes and classes within the same Assembly (and naturally from the base class it's declared in).

 

57. What's the top .NET class that everything is derived from?
System.Object.

 

58. What's the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation.  Strings are immutable, so each time it's being operated on, a new instance is created.

 

59. Can you store multiple data types in System.Array?
No.

 

60. What's the .NET class that allows the retrieval of a data element using a unique key?
HashTable.

 

61. Will the finally block get executed if an exception has not occurred?
Yes.

 

62. What's an abstract class?
A class that cannot be instantiated.  An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.


63. When do you absolutely have to declare a class as abstract?
 1.       When at least one of the methods in the class is abstract.
 2.       When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.

 

64. What's an interface?
It's an abstract class with public abstract methods all of which must be implemented in the inherited classes.

 

65. Why can't you specify the accessibility modifier for methods inside the interface?
They all must be public.  Therefore, to prevent you from getting the false impression that you have any freedom of choice,   

you are not allowed to specify any accessibility, it's public by default.

 

66. What's the difference between an interface and abstract class?
In an interface class, all methods must be abstract.  In an abstract class some methods can be concrete.  In an interface class, no accessibility modifiers are allowed, which is ok in an abstract class.

 

67. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class.  Overloading a method simply  involves

having another method with the same name within the class.

 

68. Can you declare an override method to be static if the original method is non-static?
No. The signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

 

69. Can you override private virtual methods?
No.  Private methods are not accessible outside the class.

 

70. Can you write a class without specifying namespace? Which namespace does it belong to by default?

Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you  wouldn't want global namespace.

71. What is a formatter?  
A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing  and decoding messages into data on the other end.

72. What are the Main Features of .NET platform?

Features of .NET Platform are :-

Common Language Runtime
Explains the features and benefits of the common language runtime, a run-time environment that manages the execution of code and provides services that simplify the development process.

Assemblies
Defines the concept of assemblies, which are collections of types and resources that form logical units of functionality. Assemblies are the fundamental units of deployment, version control, reuse, activation scoping, and security permissions.

Application Domains
Explains how to use application domains to provide isolation between applications.

Runtime Hosts
Describes the runtime hosts supported by the .NET Framework, including ASP.NET, Internet Explorer, and shell executables.

Common Type System
Identifies the types supported by the common language runtime.

Metadata and Self-Describing Components
Explains how the .NET Framework simplifies component interoperation by allowing compilers to emit additional declarative information, or metadata, into all modules and assemblies.

Cross-Language Interoperability
Explains how managed objects created in different programming languages can interact with one another.

.NET Framework Security
Describes mechanisms for protecting resources and code from unauthorized code and unauthorized users.

.NET Framework Class Library
Introduces the library of types provided by the .NET Framework, which expedites and optimizes the development process and gives you access to system functionality.

73. What is the use of JIT ?
JIT (Just - In - Time) is a compiler which converts MSIL code to Native Code (ie.. CPU-specific code that runs on the same computer architecture).

Because the common language runtime supplies a JIT compiler for each supported CPU architecture, developers can write a set of MSIL that can be JIT-compiled and run on computers with different architectures. However, your managed code will run only on a specific operating system if it calls platform-specific native APIs, or a platform-specific class library.

JIT compilation takes into account the fact that some code might never get called during execution. Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as needed during execution and stores the resulting native code so that it is accessible for subsequent calls. The loader creates and attaches a stub to each of a type's methods when the type is loaded. On the initial call to the method, the stub passes control to the JIT compiler, which converts the MSIL for that method into native code and modifies the stub to direct execution to the location of the native code. Subsequent calls of the JIT-compiled method proceed directly to the native code that was previously generated, reducing the time it takes to JIT-compile and run the code.

75. What is GUID , why we use it and where?
GUID :-- GUID is Short form of Globally Unique Identifier, a unique 128-bit number that is produced by the Windows OS or by some Windows applications to identify a particular component, application, file, database entry, and/or user. For instance, a Web site may generate a GUID and assign it to a user's browser to record and track the session. A GUID is also used in a Windows registry to identify COM DLLs. Knowing where to look in the registry and having the correct GUID yields a lot information about a COM object (i.e., information in the type library, its physical location, etc.). Windows also identifies user accounts by a username (computer/domain and username) and assigns it a GUID. Some database administrators even will use GUIDs as primary key values in databases.

GUIDs can be created in a number of ways, but usually they are a combination of a few unique settings based on specific point in time (e.g., an IP address, network MAC address, clock date/time, etc.).

76. Describe the difference between inline and code behind - which is best in a loosely coupled solution
ASP.NET supports two modes of page development: Page logic code that is written inside runat="server"> blocks within an .aspx file and dynamically compiled the first time the page is requested on the server. Page logic code that is written within an external class that is compiled prior to deployment on a server and linked ""behind"" the .aspx file at run time.

77. Whats MSIL, and why should my developers need an appreciation of it if at all?
When compiling the source code to managed code, the compiler translates the source into Microsoft intermediate language (MSIL). This is a CPU-independent set of instructions that can efficiently be converted to native code. Microsoft intermediate language (MSIL) is a translation used as the output of a number of compilers. It is the input to a just-in-time (JIT) compiler. The Common Language Runtime includes a JIT compiler for the conversion of MSIL to native code.

Before Microsoft Intermediate Language (MSIL) can be executed it, must be converted by the .NET Framework just-in-time (JIT) compiler to native code. This is CPU-specific code that runs on the same computer architecture as the JIT compiler. Rather than using time and memory to convert all of the MSIL in a portable executable (PE) file to native code. It converts the MSIL as needed whilst executing, then caches the resulting native code so its accessible for any subsequent calls.

78. How many .NET languages can a single .NET DLL contain?
One

79. What type of code (server or client) is found in a Code-Behind class?
Server

80. What is Globalizationa and Localization ?
Globalization is the process of creating an application that meets the needs of users from multiple cultures. It includes using the correct
currency, date and time format, calendar, writing direction, sorting rules, and other issues. Accommodating these cultural differences in an application is called localization.Using classes of System.Globalization namespace, you can set application's current culture.

This can be achieved by using any of the following 3 approaches.
      1.      Detect and redirect
      2.      Run-time adjustment
      3.      Using Satellite assemblies.
     
81. Whate are Resource Files ? How are they used in .NET?
Resource files are the files containing data that is logically deployed with an application.These files can contain data in a number of formats including strings, images and persisted objects. It has the main advantage of If we store data in these files then we don't need to compile these if the data get changed. In .NET we basically require them storing culture specific informations by localizing application's resources. You can deploy your resources using satellite assemblies.

82. Describe the difference between a Thread and a Process?
A Process is an instance of an running application. And a thread is the Execution stream of the Process. A process can have multiple Thread.
When a process starts a specific memory area is allocated to it. When there is multiple thread in a process, each thread gets a memory for storing the variables in it and plus they can access to the global variables which is common for all the thread. Eg.A Microsoft Word is a Application. When you open a word file,an instance of the Word starts and a process is allocated to this instance which has one thread.

83. What is the difference between an EXE and a DLL?
You can create an objects of Dll but not of the EXE.
Dll is an In-Process Component whereas EXE is an OUt-Process Component.
Exe is for single use whereas you can use Dll for multiple use.
Exe can be started as standalone where dll cannot be.

84. What is strong-typing versus weak-typing? Which is preferred? Why?
Strong typing implies that the types of variables involved in operations are associated to the variable, checked at compile-time, and require explicit conversion; weak typing implies that they are associated to the value, checked at run-time, and are implicitly converted as required. (Which is preferred is a disputable point, but I personally prefer strong typing because I like my errors to be found as soon as possible.)

85. What is a PID? How is it useful when troubleshooting a system?
PID is the process Id of the application in Windows. Whenever a process starts running in the Windows environment, it is associated with an individual process Id or PID.

The PID (Process ID) a unique number for each item on the Process Tab, Image Name list. How do you get the PID to appear? In Task Manger, select the View menu, then select columns and check PID (Process Identifier).

In Linux, PID is used to debug a process explicitly. However we cannot do this in a windows environment.

Microsoft has launched a SDK called as Microsoft Operations Management (MOM). This uses the PID to find out which dll's have been loaded by a process in the memory. This is essentially helpful in situations where the Process which has a memory leak is to be traced to a erring dll. Personally I have never used a PID, our Windows debugger does the things required to find out.

86. Describe what an Interface is and how it's different from a Class.
An interface is a structure of code which is similar to a class. An interface is a prototype for a class and is useful from a logical design perspective. Interfaces provide a means to define the protocols for a class without worrying about the implementation details. The syntax for creating interfaces follows:
interface Identifier {
  InterfaceBody
}

Identifier is the name of the interface and InterfaceBody refers to the abstract methods and static final variables that make up the interface. Because it is assumed that all the methods in an interface are abstract, it isn't necessary to use the abstract keyword

An interface is a description of some of the members available from a class. In practice, the syntax typically looks similar to a class definition, except that there's no code defined for the methods — just their name, the arguments passed and the type of the value returned.
So what good is it? None by itself. But you create an interface so that classes will implement it.

But what does it mean to implement an interface. The interface acts as a contract or promise. If a class implements an interface, then it must have the properties and methods of the interface defined in the class. This is enforced by the compiler.

Broadly the differentiators between classes and interfaces is as follows
• Interface should not have any implementation.
• Interface can not create any instance.
• Interface should provide high level abstraction from the implementation.
• Interface can have multiple inheritances.
• Default access level of the interface is public.

87. What is the difference between XML Web Services using ASMX and .NET Remoting using SOAP?
ASP.NET Web services and .NET Remoting provide a full suite of design options for cross-process and cross-plaform communication in distributed applications. In general, ASP.NET Web services provide the highest levels of interoperability with full support for WSDL and SOAP over HTTP, while .NET Remoting is designed for common language runtime type-system fidelity and supports additional data format and communication channels. Hence if we looking cross-platform communication than web services is the choice coz for .NET remoting .Net framework is requried which may or may not present for the other platform.

88. What are PDBs? Where must they be located for debugging to work?
A program database (PDB) files holds debugging and project state information that allows incremental linking of debug configuration of your program.There are several different types of symbolic debugging information. The default type for Microsoft compiler is the so-called PDB file. The compiler setting for creating this file is /Zi, or /ZI for C/C++(which creates a PDB file with additional information that enables a feature called ""Edit and Continue"") or a Visual Basic/C#/JScript .NET program with /debug.

A PDB file is a separate file, placed by default in the Debug project subdirectory, that has the same name as the executable file with the extension .pdb. Note that the Visual C++ compiler by default creates an additional PDB file called VC60.pdb for VisulaC++6.0 and VC70.PDB file for VisulaC++7.0. The compiler creates this file during compilation of the source code, when the compiler isn't aware of the final name of the executable. The linker can merge this temporary PDB file into the main one if you tell it to, but it won't do it by default. The PDB file can be useful to display the detailed stack trace with source files and line numbers.

89. What is FullTrust? Do GAC'ed assemblies have FullTrust?
Before the .NET Framework existed, Windows had two levels of trust for downloaded code. This old model was a binary trust model. You only had two choices: Full Trust, and No Trust. The code could either do anything you could do, or it wouldn't run at all.
 
The permission sets in .NET include FullTrust, SkipVerification, Execution, Nothing, LocalIntranet, Internet and Everything. Full Trust Grants unrestricted permissions to system resources. Fully trusted code run by a normal, nonprivileged user cannot do administrative tasks, but can access any resources the user can access, and do anything the user can do. From a security standpoint, you can think of fully trusted code as being similar to native, unmanaged code, like a traditional ActiveX control.
GAC assemblies are granted FullTrust. In v1.0 and 1.1, the fact that assemblies in the GAC seem to always get a FullTrust grant is actually a side effect of the fact that the GAC lives on the local machine.  If anyone were to lock down the security policy by changing the grant set of the local machine to something less than FullTrust, and if your assembly did not get extra permission from some other code group, it would no longer have FullTrust even though it lives in the GAC.

90. What does this do? gacutil /l | find /i "Corillian"
The Global Assembly Cache tool allows you to view and manipulate the contents of the global assembly cache and download cache.The tool comes with various optional params to do that.
""/l"" option Lists the contents of the global assembly cache. If you specify the assemblyName parameter(/l [assemblyName]), the tool lists only the assemblies matching that name.

91. What does this do .. sn -t foo.dll ?
Sn -t option displays the token for the public key stored in infile. The contents of infile must be previously generated using -p.
Sn.exe computes the token using a hash function from the public key. To save space, the common language runtime stores public key tokens in the manifest as part of a reference to another assembly when it records a dependency to an assembly that has a strong name. The -tp option displays the public key in addition to the token.

What is the difference between a Debug and Release build? Is there a significant speed difference? Why or why not?
The Debug build is the program compiled with full symbolic debug information and no optimization. The Release build is the program compiled employing  optimization and contains no symbolic debug information. These settings can be changed as per need from Project Configuration properties. The release runs faster since it does not have any debug symbols and is optimized.

92. Explain the use of virtual, sealed, override, and abstract.
Abstract: The keyword can be applied for a class or method.
1. Class: If we use abstract keyword for a class it makes the
class an abstract class, which means it cant be instantiated. Though
it is not nessacary to make all the method within the  abstract class to be virtual. ie, Abstract class can have concrete methods
2. Method: If we make a method as abstract, we dont need to provide implementation
of the method in the class but the derived class need to implement/override this method.
 
Sealed: It can be applied on a class and methods. It stops the type from further derivation i.e no one can derive class
from a sealed class,ie A sealed class cannot be inherited.A sealed class cannot be a abstract class.A compile time error is thrown if you try to specify sealed class as a  base class.
When an instance method declaration includes a sealed modifier, that method is said to be a sealed method. If an instance method declaration includes the sealed modifier, it must also include the override modifier. Use of the sealed modifier prevents a derived class from further overriding the method  For Egs: sealed override public void Sample() { Console.WriteLine("Sealed Method"); }


Virtual & Override: Virtual & Override keywords provides runtime polymorphism. A base class can make some of its methods
as virtual which allows the derived class a chance to override the base class implementation by using override keyword.
 
For e.g. class Shape
  {
  int a
  public virtual void Display()
  {
   Console.WriteLine("Shape");
  }
 }
 
 class Rectangle:Shape
 {
  public override void Display()
  {
   Console.WriteLine("Derived");
  }
 }
93 What is difference between MetaData and Manifest ?
Metadata and Manifest forms an integral part of an assembly( dll / exe ) in .net framework .
Out of which Metadata is a mandatory component , which as the name suggests gives the details about various components of IL code viz : Methods , properties , fields , class etc.

Essentially Metadata maintains details in form of tables like Methods Metadata tables , Properties Metadata tables , which maintains the list of given type and other details like access specifier , return type etc.

Now Manifest is a part of metadata only , fully called as "manifest metadata tables" , it contains the details of the references needed by the assembly of any other external assembly / type , it could be a custom assembly or standard System namespace .

94. Why only boxed types can be unboxed?
Unboxing is the process of converting a Reference type variable to Value type and thus allocating memory on the stack . It happens only to those Reference type variables that have been earlier created by Boxing of a Value Type , therefore internally they contain a value type , which can be obtained through explicit casting . For any other Reference type , they don't internally contain a Value type to Unboxed via explicit casting . This is why only boxed types can be unboxed .

95 What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional   integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request  object. Sure, there are workarounds, but they're difficult. Finally, Response.Redirect  necessitates a round trip to the client, which, on high-volume sites, causes scalability problems.
As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.

Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.

Response.Dedirect() :client know the physical location (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they're difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.

 96. What are Web Services?
Web services are small, reusable applications that help computers from many different operating system platforms work together by exchanging messages. Web services are based on industry protocols that include XML (Extensible Markup Language), SOAP (Simple Object Access Protocol), and WSDL (Web Services Description Language). These protocols help computers work together across platforms and programming languages.

From a business perspective, Web services are used to reenable information technology so that it can change, move, and adapt like other aspects of a business.  They not only connect systems, they can help connect people with the information they need, within the software applications they are used to using, and wherever they happen to be.

Microsoft offers a complete range of software that helps organizations and individuals benefit from Web service-based connectivity. These include theMicrosoft Visual Studio .NET 2003 developer tools, the Windows Server System that hosts Web services, and familiar desktop applications such as the Microsoft Office System that "consume" Web services.

99. What are the Benefits of .NET?

.NET technologies use Web services to help enhance the computing experience with highly integrated communications and information. Because .NET includes the core technologies for building Web services, it benefits everyone: individual users, organizations, and developers.
•   .NET benefits organizations by helping them get the most out of their existing technology investments while creating new ways to implement powerful, cost-effective information technology that will meet future needs. .NET technologies and Web services can be used to integrate even the most disparate computing environments. .NET frees organizations from the confines of proprietary technology, providing the flexibility and scalability that can help organizations connect their existing IT systems and build a foundation for the next wave of computer technology. .NET and Web services can help organizations lower operating costs by helping connect systems; increase sales by helping employees access the right information when and where they need it; integrate services and applications with customers and partners; and lower the costs of information technology with tools that help developers quickly create new solutions to address business issues.
•   .NET benefits individuals by helping provide a more personal and integrated computing experience. .NET-enabled computing is centered on the user–not on the features of the software or hardware. The user's experience becomes very customizable and provides integrated data and customized interactions that work well with a wide range of computing hardware, such as Pocket PCs, Smartphones, laptops, and other devices. The .NET-based experience enhances the mobile computing experience so user's can get their information regardless of their location. For example, it can take place on a desktop computer, in the car on a Smartphone, or at the store on a Pocket PC.
•   .NET benefits developers by providing a tightly integrated set of tools for building and integrating Web services. Visual Studio .NET and the .NET Framework provide comprehensive development platforms that offer the best, fastest, and most cost-effective way to build Web services. With Visual Studio .NET and the .NET Framework, developers can take advantage of a programming model designed from the ground up for creating Web services in a highly productive, multilanguage environment. With scalable, high-performance execution, the .NET tools allow developers to use existing skills to create a wide range of solutions that work across a broad array of computing devices. .NET also provides a foundation for building Service Oriented Architectures (SOA).
 
1. What are Service Oriented Architectures (SOA)?

SOA describes an information technology architecture that enables distributed computing environments with many different types of computing platforms and applications. Web services are one of the technologies that help make SOAs possible. As a concept, SOA has been around since the 1980s, but many early IT technologies failed to achieve the goal of linking different types of applications and systems. By making early investments with .NET, Microsoft has helped provide the building blocks that today are putting many enterprise customers on the path to successfully implementing SOAs. With SOAs, companies can benefit from the unimpeded flow of information that is the hallmark of connected systems.
 
2. What are Web Services Enhancements for Microsoft .NET (WSE)?

WSE is an add-on to Microsoft Visual Studio .NET and the Microsoft .NET Framework that helps developers build greater security features into Web services using the latest Web services protocol specifications and standards. With WSE 2.0 developers can create security-enhanced connected systems that help improve business processes within–and beyond–corporate trust boundaries and create new revenue-generating opportunities.
 
3. What is a Smart Client?
Smart clients are client applications that consume Web services and reside on user hardware such as desktop PCs, laptops, Pocket PCs, and Smartphones. They are easily deployed and managed and provide an adaptive, responsive, and rich interactive experience by taking advantage of the computing resources on the device and intelligently connecting to distributed data sources.
 
4. What is .NET Passport?
.NET Passport is a Web-based service that is designed to make signing in to Web sites fast and easy. Passport enables participating sites to authenticate a user with a single set of sign-in credentials, alleviating the need for users to remember numerous passwords and user names.
 
5. What are the Current Microsoft Products and Technologies That Use .NET?
Microsoft .NET provides everything that is needed to develop and deploy a Web service-based IT architecture: servers to host Web services; development tools to create Web services; applications to use them; and a network of more than 35,000 Microsoft partners to help organizations deploy and manage them. .NET technologies are supported throughout the family of Microsoft products, including the Windows Server System, the Windows XP desktop operating system, and the Microsoft Office System. And .NET technologies will play an even larger role in future versions of Microsoft products.
 
6. Who is Using .NET?
Organizations worldwide are implementing .NET technologies and Web services to create connected businesses and to help individuals communicate and collaborate more effectively. For example, Honeywell, GlaxoSmithKline, Sony, Dollar Rent A Car, Farmers Insurance, and the United States Postal Service are just a few of the well-known names that are using .NET. To read more about .NET technology in use today, visit the Microsoft .NET Case Study site.
 
7. How Do I Find a Microsoft Partner to Help Me Connect My Organization Using .NET?
Microsoft Certified Partners are independent companies that can provide you with the highest levels of technical expertise, strategic thinking, and hands-on skills. Microsoft Certified Partners encompass a broad range of expertise and vendor affiliations. Their real-world perspective can help you prioritize and effectively deliver your technology solutions.

 

8. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process.
inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.
 
9. What's the difference between Response.Write() andResponse.Output.Write()?
Response.Output.Write() allows you to write formatted output.
 
10. What methods are fired during the page load?
Init() - when the page is instantiated
Load() - when the page is loaded into server memory
PreRender() - the brief moment before the page is displayed to the user as HTML
Unload() - when page finishes loading.
 
11. When during the page processing cycle is ViewState available?
After the Init() and before the Page_Load(), or OnLoad() for a control.

 12. What namespace does the Web page belong in the .NET Framework class hierarchy?
System.Web.UI.Page
 
13. Where do you store the information about the user's locale?
System.Web.UI.Page.Culture
 
14. What's the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?
CodeBehind is relevant to Visual Studio.NET only.
 
15. What's a bubbled event?
When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
 
16. Suppose you want a certain ASP.NET function executed on MouseOver for a certain button.  Where do you add an event handler?
Add an OnMouseOver attribute to the button.  Example: btnSubmit.Attributes.Add("onmouseover","someClientCodeHere();");
 
17. What data types do the RangeValidator control support?
Integer, String, and Date.
 
18. Explain the differences between Server-side and Client-side code?
Server-side code executes on the server.  Client-side code executes in the client's browser.
 
19. What type of code (server or client) is found in a Code-Behind class?
The answer is server-side code since code-behind is executed on the server.  However, during the code-behind's execution on the server, it can render client-side code such as JavaScript to be processed in the clients browser.  But just to be clear, code-behind executes on the server, thus making it server-side code.

20. Should user input data validation occur server-side or client-side?  Why?
All user input data validation should occur on the server at a minimum.  Additionally, client-side validation can be performed where deemed appropriate and feasable to provide a richer, more responsive experience for the user.
 
21. What is the difference between Server.Transfer and Response.Redirect?  Why would I choose one over the other?
Server.Transfer transfers page processing from one page directly to the next page without making a round-trip back to the client's browser.  This provides a faster response with a little less overhead on the server.  Server.Transfer does not update the clients url history list or current url.  Response.Redirect is used to redirect the user's browser to another page or site.  This performas a trip back to the client where the client's browser is redirected to the new page.  The user's browser history list is updated to reflect the new address.
 
22. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
Valid answers are:
·  A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
·  A DataSet is designed to work without any continuing connection to the original data source.
·  Data in a DataSet is bulk-loaded, rather than being loaded on demand.
·  There's no concept of cursor types in a DataSet.
·  DataSets have no current record pointer You can use For Each loops to move through the data.
·  You can store many edits in a DataSet, and write them to the original data source in a single operation.
·  Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
 
23. What is the Global.asax used for?
The Global.asax (including the Global.asax.cs file) is used to implement application and session level events.
 
24. What are the Application_Start and Session_Start subroutines used for?
This is where you can set the specific variables for the Application and Session objects.
 
25. Can you explain what inheritance is and an example of when you might use it?

When you want to inherit (use the functionality of) another class.  Example: With a base class named Employee, a Manager class could be derived from the Employee base class.
 
26. Whats an assembly?
Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN
 
27. Describe the difference between inline and code behind.
Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page.
 
28.Explain what a diffgram is, and a good use for one?

The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML.  A good use is reading database data to an XML file to be sent to a Web Service.
 
29. Whats MSIL, and why should my developers need an appreciation of it if at all?
MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL.  MSIL also allows the .NET Framework to JIT compile the assembly on the installed computer.
 
30. Which method do you invoke on the DataAdapter control to load your generated dataset with data?

The Fill() method.
 
31. Can you edit data in the Repeater control?
No, it just reads the information from its data source.
 
32. Which template must you provide, in order to display data in a Repeater control?
ItemTemplate.
 
33. How can you provide an alternating color scheme in a Repeater control?
Use the AlternatingItemTemplate.
 
34 What property must you set, and what method must you call in your code, in order to bind the data from a data source to the Repeater control?
You must set the DataSource property and call the DataBind method.
 
35. What base class do all Web Forms inherit from?
The Page class.
 
36. Name two properties common in every validation control?
ControlToValidate property and Text property.
 
37. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
DataTextField property.
 
38. Which control would you use if you needed to make sure the values in two different controls matched?
CompareValidator control.
 
39. How many classes can a single .NET DLL contain?
It can contain many classes.

 

 

@@@@Difference between :  Unique index vs Primary Key @@@@


1. Primary Key makes sure the COLUMN values are not NULL while Unique
Constraint does not.
2. When creating a Primary key an Unique Index is created and NOT Vice Versa
3. Primary Keys cannot be deleted when reference by a Foriegn Key and Unique
constriants can be deleted irrespective of references.
4. There can be only one Primary Key in the table, You can have multiple unique
constraints on the table.
5. While creating a Primary Key Clustered Index is created by default where as during
the creation of a Unique Constraint a non-clustered Index is created by default.


1.    What's the difference between Response.Write() andResponse.Output.Write()?
The latter one allows you to write formattedoutput.

2.    Where do you store the information about the user's locale?
System.Web.UI.Page.Culture

3.    What's the difference between Codebehind="MyCode.aspx.cs" and Src="MyCode.aspx.cs"?
CodeBehind is relevant to Visual Studio.NET only.

4.    What's a bubbled event?
When you have a complex control, likeDataGrid, writing an event processing routine for each object (cell, button,row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
Suppose you want a certain ASP.NET function executed on MouseOver over a certain button.

5.    Where do you add an event handler?
It's the Attributesproperty, the Add function inside that property.            
e.g. btnSubmit.Attributes.Add("onMouseOver","someClientCode();")

6.    What data type does the RangeValidator control support?
Integer,String and Date.

7.    What are the different types of caching?
Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In context of web application, caching is used to retain the pages or data across HTTP requests and reuse them without the expense of recreating them.ASP.NET has 3 kinds of caching strategiesOutput CachingFragment CachingData    

CachingOutput Caching: Caches the dynamic output generated by a request. Some times it is useful to cache  the output of a website even for a minute, which will result in a better  performance. For caching the whole page the page should have OutputCache directive.<%@ OutputCache Duration="60" VaryByParam="state" %>

Fragment Caching: Caches the portion of the  page generated by the request. Some times it is not practical to cache the entire page, in such cases we can cache a portion of page<%@ OutputCache Duration="120" VaryByParam="CategoryID;SelectedID"%>

Data Caching: Caches the objects programmatically. For  data caching asp.net provides a cache object for eg: cache["States"] = dsStates;

8. What do you mean by authentication and authorization?
Authentication is the process of validating a user on the credentials (username and     password) and authorization performs after authentication. After Authentication a user will be verified for performing the various tasks, It access is limited it is known as  authorization.

9.
What are different types of directives in .NET?
@Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can       be included only in .aspx files <%@ Page AspCompat="TRUE" language="C#" %>  
@Control:Defines control-specific attributes used by the ASP.NET page parser and        compiler. Can be included only in .ascx files. <%@ Control Language="VB" EnableViewState="false" %>
@Import: Explicitly imports a namespace into a page or user control. The Import         directive cannot have more than one namespace attribute. To import multiple     namespaces,     use multiple @Import directives. <% @ Import Namespace="System.web" %>
@Implements: Indicates that the current page or user control implements the specified .NET      framework interface.<%@ Implements Interface="System.Web.UI.IPostBackEventHandler" %>
@Register: Associates aliases with namespaces and class names for concise notation in   custom server control syntax.<%@ Register Tagprefix="Acme" Tagname="AdRotator" Src="AdRotator.ascx" %>
@Assembly: Links an assembly to the current page during compilation, making all   the     assembly's classes and interfaces available for use on the      page. <%@ Assembly Name="MyAssembly" %><%@ Assembly Src="MySource.vb" %>
@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a        user control contained in a page<%@ OutputCache Duration="#ofseconds" Location="Any | Client | Downstream | Server | None" Shared="True | False" VaryByControl="controlname" VaryByCustom="browser | customstring" VaryByHeader="headers" VaryByParam="parametername" %>
@Reference: Declaratively indicates that another user control or page source file               should be dynamically compiled and linked against the page in which this directive is   declared.

1. How do I debug an ASP.NET application that wasn't written with Visual Studio.NET and that doesn't use code-behind?
Start the DbgClr debugger that comes with the .NET Framework SDK, open the file containing      the code you want to debug, and set your breakpoints. Start the ASP.NET application. Go back to DbgClr, choose Debug Processes from the Tools menu, and select  aspnet_wp.exe from  the list of processes. (If aspnet_wp.exe doesn't appear in the list,check the "Show system      processes" box.) Click the Attach button to attach to aspnet_wp.exe and begin debugging.
Be sure to enable debugging in the ASPX file before debugging it with DbgClr. You can   enable tell ASP.NET to build debug executables by placing a
<%@ Page Debug="true" %>   statement at the top of an ASPX file or a   <COMPILATION debug="true" />statement in a Web.config file.
 
2. Can a user browsing my Web site read my Web.config or Global.asax files?
No. The <HTTPHANDLERS>section of Machine.config, which holds the master configuration  settings for ASP.NET, contains entries that map ASAX files, CONFIG files, and selected  other file types to an HTTP handler named HttpForbiddenHandler, which fails attempts to retrieve the associated file. You can modify it by editing  Machine.config or including an section in a local Web.config file.

3. What's the difference between Page.RegisterClientScriptBlock and Page.RegisterStartupScript?
RegisterClientScriptBlock is for returning blocks of client-side script containing functions. RegisterStartupScript is for returning blocks of client-script not   packaged in functions-in other words, code that's to execute when the page is loaded. The latter positions script blocks near the end of the document so elements on the page that the script interacts are loaded before the script runs.<%@ Reference Control="MyControl.ascx" %>

4. Is it necessary to lock application state before accessing it?
Only if you're performing a multistep update and want the update to be treated as an atomic     operation. Here's an example:
                Application.Lock ();
                Application["ItemsSold"] = (int) Application["ItemsSold"] + 1;
                Application["ItemsLeft"] = (int) Application["ItemsLeft"] - 1;
                Application.UnLock (); 
By locking application state before updating it and unlocking it afterwards, you ensure  that another request being processed on another thread doesn't read application state   at exactly the wrong time and see an inconsistent view of it. If I update session state, should I lock it, too? Are concurrent accesses by multiple requests executing on multiple threads a concern with session state?
Concurrent accesses aren't an issue with session state, for two reasons. One, it's unlikely that two requests from the same user will overlap. Two, if they do overlap, ASP.NET locks down session state during request processing so that two threads can't touch it at once. Session state is locked down when the HttpApplication instance that's processing the request fires an AcquireRequestState event and unlocked when it fires a ReleaseRequestState event.

5. What are VSDISCO files?

VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns   references to all ASMX and DISCO files in the host directory and any subdirectories not  noted in <exclude> elements:
             <?xml version="1.0" ?>
                <dynamicDiscovery
                  xmlns="urn:schemas-dynamicdiscovery:disco.2000-03-17">
                  <exclude path="_vti_cnf" />
                  <exclude path="_vti_pvt" />
                  <exclude path="_vti_log" />
                  <exclude path="_vti_script" />
                  <exclude path="_vti_txt" />
                </dynamicDiscovery>  

6. How does dynamic discovery work?
ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host  directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line   in the <httpHandlers> section of Machine.config that maps *.vsdisco to System.Web.Services.Discovery.DiscoveryRequestHandler and granting the ASPNET  user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
 
7. Is it possible to prevent a browser from caching an ASPX page?
Just call SetNoStore on the HttpCachePolicy object exposed through the Response object's Cache property, as demonstrated here:
 
        <%@ Page Language="C#" %>
        <html>
          <body>
            <%
              Response.Cache.SetNoStore ();
              Response.Write (DateTime.Now.ToLongTimeString ());
            %>
          </body>
        </html> 

SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time.

8. What does AspCompat="true" mean and when should I use it?
AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects--that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with  Visual Basic 6.0. AspCompat should also be set to true (regardless of threading  model)  if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:

         <%@ Page AspCompat="true" %> 

Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available      to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the  request for the page) and the COM objects it creates share an apartment. AspCompat="true" forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat="true," request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it's  marshaled across apartment boundaries.

Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don't access ASP intrinsic objects and that are registered ThreadingModel=Free or  ThreadingModel=Both.

9. What are ASP.NET Web Forms? How is this technology different than what is available though ASP?
Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto  them. However, these UI elements render themselves in the appropriate markup language   required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.

10. What event handlers can I include in Global.asax?
Application_Start,Application_End, Application_AcquireRequestState, Application_AuthenticateRequest, Application_AuthorizeRequest, Application_BeginRequest, Application_Disposed,  Application_EndRequest, Application_Error, Application_PostRequestHandlerExecute, Application_PreRequestHandlerExecute,
Application_PreSendRequestContent, Application_PreSendRequestHeaders, Application_ReleaseRequestState, Application_ResolveRequestCache, Application_UpdateRequestCache, Session_Start,Session_End
You can optionally include "On" in any of method names. For example, you can name a BeginRequest event handler.Application_BeginRequest or Application_OnBeginRequest.You can also include event handlers in Global.asax for events fired by custom HTTP modules.Note that not all of the event handlers make sense for Web Services (they're designed for ASP.NET applications in general, whereas .NET XML Web Services are specialized instances of an ASP.NET app). For example, the Application_AuthenticateRequest and Application_AuthorizeRequest events are designed to be used with ASP.NET Forms authentication. 

11. What is different b/w  webconfig.xml & Machineconfig.xml
Web.config & machine.config both are configuration files.Web.config contains settings specific to an application where as machine.config contains settings to a computer. The Configuration system first searches settings in machine.config file & then looks in application configuration  files.Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. There is only Machine.config file on a web server.

If I'm developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
Use the state server or store the state in the database. This can be easily done through simple setting change in the web.config.
<SESSIONSTATE
StateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1; user id=sa; password="
cookieless="false"
timeout="30"
/>You can specify mode as "stateserver" or "sqlserver".

Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
"One of ASP.NET's most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.

12. How do you create a permanent cookie?
Permanent cookies are available until a specified expiration date, and are stored on the hard disk.So Set the 'Expires' property any value greater than DataTime.MinValue with respect to the current datetime. If u want the cookie which never expires set its Expires property equal to DateTime.maxValue.

13. Which method do you use to redirect the user to another page without performing a round trip to the client?
Server.Transfer and Server.Execute

14. What property do you have to set to tell the grid which page to go to when using the Pager object?
CurrentPageIndex

15. What does the "EnableViewState" property do? Why would I want it on or off?
Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip, then you do not need the control to maintain it's view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.

16. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
The Application_Start event is guaranteed to occur only once throughout the lifetime of the application. It's a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.

17. What are the advantages and  disadvantages of viewstate?
The primary advantages of the ViewState feature in ASP.NET are:

1. Simplicity. There is no need to write possibly complex code to store form data between page submissions.
2. Flexibility. It is possible to enable, configure, and disable ViewState on a control-by-control basis, choosing to persist the values of some fields but not others.

There are, however a few disadvantages that are worth pointing out:

1. Does not track across pages. ViewState information does not automatically transfer from page to page. With the session
approach, values can be stored in the session and accessed from other pages. This is not possible with ViewState, so storing
data into the session must be done explicitly.

2. ViewState is not suitable for transferring data for back-end systems. That is, data still has to be transferred to the back
end using some form of data object.

18. Describe session handling in a webfarm, how does it work and what are the limits?
ASP.NET Session supports storing of session data in 3 ways, i] in In-Process ( in the same memory that ASP.NET uses) , ii] out-of-process using Windows NT Service )in separate memory from ASP.NET ) or iii] in SQL Server (persistent storage). Both the Windows Service and SQL Server solution support a webfarm scenario where all the web-servers can be configured to share common session state store.
 
. Windows Service :
We can start this service by Start | Control Panel | Administrative Tools | Services | . In that we service names  ASP.NET State Service. We can start or stop service by manually or configure to start automatically. Then we have to configure our web.config file


<CONFIGURATION><configuration>
 <system.web>
  <SessionState
   mode = "StateServer"
   stateConnectionString = "tcpip=127.0.0.1:42424"
   stateNetworkTimeout = "10"
   sqlConnectionString="data source = 127.0.0.1; uid=sa;pwd="
   cookieless ="Flase"
   timeout= "20" />
 </system.web>
</configuration> </SYSTEM.WEB>
</CONFIGURATION>
Here ASP.Net Session is directed to use Windows Service for state management on local server (address : 127.0.0.1 is TCP/IP loop-back address). The default port is 42424. we can configure to any port but for that we have to manually edit the registry.
 Follow these simple steps
- In a webfarm make sure you have the same config file in all your web servers.
- Also make sure your objects are serializable.
- For session state to be maintained across different web servers in the webfarm, the application path of the web-site in the IIS Metabase should be identical in all the web-servers in the webfarm.

19. When do you set "<IDENTITY impersonate="true" />" ?
Identity is a webconfig declaration under System.web, which helps to control the application Identity of the web applicaton. Which can be at any level(Machine,Site,application,subdirectory,or page), attribute impersonate with "true" as value specifies that client impersonation is used

20. What are different templates available in Repeater,DataList and Datagrid ?
Templates enable one to apply complicated formatting to each of the items displayed by a control.Repeater control supports five types of templates.HeaderTemplate controls  how the header of the repeater control is formatted.ItemTemplate controls the formatting of each  item displayed.AlternatingItemTemplate controls how alternate items are formatted and the  SeparatorTemplate displays a separator between each item displyed.FooterTemplate is used for  controlling how the footer of the repeater control is formatted.The DataList and Datagrid supports two templates in addition to the above five.SelectedItem Template controls how a selected item is  formatted and EditItemTemplate controls how an item selected for editing is formatted.

21. What is the sequence of operation takes place when a page is loaded?
BeginTranaction  - only if the request is transacted
Init    - every time a page is processed
LoadViewState  - Only on postback
ProcessPostData1  - Only on postback
Load    - every time
ProcessData2   - Only on Postback
RaiseChangedEvent  - Only on Postback
RaisePostBackEvent  - Only on Postback
PreRender   - everytime
BuildTraceTree  - only if tracing is enabled
SaveViewState  - every time
Render   - Everytime
End Transaction  - only if the request is transacted
Trace.EndRequest  - only when tracing is enabled
UnloadRecursive  - Every request

22. What are the various ways of securing a web site that could prevent from hacking etc .. ?
1) Authentication/Authorization
2) Encryption/Decryption
3) Maintaining web servers outside the corporate firewall. etc.,

23. What is the difference between in-proc and out-of-proc?
An inproc is one which runs in the same process area as that of the client giving tha advantage of speed but the disadvantage of stability becoz if it crashes it takes the client application also with it.Outproc is one which works outside the clients memory thus giving stability to the client, but we have to compromise a bit on speed.

24. What does aspnet_regiis -i do ?
Aspnet_regiis.exe is The ASP.NET IIS Registration tool allows an administrator or installation program to easily update the script maps for an ASP.NET application to point to the ASP.NET ISAPI version associated with the tool. The tool can also be used to display the status of all installed versions of ASP. NET, register the ASP.NET version coupled with the tool, create client-script directories, and perform other configuration operations.
 
When multiple versions of the .NET Framework are executing side-by-side on a single computer, the ASP.NET ISAPI version mapped to an ASP.NET application determines which version of the common language runtime is used for the application.
 
The tool can be launched with a set of optional parameters. Option "i" Installs the version of ASP.NET associated with Aspnet_regiis.exe and updates the script maps at the IIS metabase root and below. Note that only applications that are currently mapped to an earlier version of ASP.NET are affected

25. What is a PostBack?

The process in which a Web page sends data back to the same page on the server.

26. What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?

ViewState is the mechanism ASP.NET uses to keep track of server control state values that don't otherwise post back as part of the HTTP form. ViewState Maintains the UI State of a Page
  ViewState is base64-encoded.
 It is not encrypted but it can be encrypted by setting EnableViewStatMAC="true" & setting the machineKey validation type to 3DES.  If you want to NOT maintain the ViewState, include the directive < %@ Page EnableViewState="false" % > at the top of an .aspx page or add the attribute EnableViewState="false" to any control.

27. What is the < machinekey > element and what two ASP.NET technologies is it used for?

Configures keys to use for encryption and decryption of forms authentication cookie data and view state data, and for verification of out-of-process session state identification.There fore 2 ASP.Net technique in which it is used are Encryption/Decryption & Verification

28. What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each?

ASP.NET provides three distinct ways to store session data for your application: in-process session state, out-of-process session state as a Windows service, and out-of-process session state in a SQL Server database. Each has it advantages. 

1.In-process session-state mode
Limitations:
 * When using the in-process session-state mode, session-state data is lost if aspnet_wp.exe or the application domain restarts.
 * If you enable Web garden mode in the < processModel > element of the application's Web.config file, do not use in-process session-state mode. Otherwise, random data loss can occur.
Advantage:
 * in-process session state is by far the fastest solution. If you are storing only small amounts of volatile data in session state, it is recommended that you use the in-process provider.

2. The State Server simply stores session state in memory when in out-of-proc mode. In this mode the worker process talks directly to the State Server

3. SQL mode, session states are stored in a SQL Server database and the worker process talks directly to SQL. The ASP.NET worker processes are then able to take advantage of this simple storage service by serializing and saving (using .NET serialization services) all objects within a client's Session collection at the end of each Web request
 Both these out-of-process solutions are useful primarily if you scale your application across multiple processors or multiple computers, or where data cannot be lost if a server or process is restarted.

29. What is the difference between HTTP-Post and HTTP-Get?

As their names imply, both HTTP GET and HTTP POST use HTTP as their underlying protocol. Both of these methods encode request parameters as name/value pairs in the HTTP request.
The GET method creates a query string and appends it to the script's URL on the server that handles the request.
The POST method creates a name/value pairs that are passed in the body of the HTTP request message.

30. Name and describe some HTTP Status Codes and what they express to the requesting client.

When users try to access content on a server that is running Internet Information Services (IIS) through HTTP or File Transfer Protocol (FTP), IIS returns a numeric code that indicates the status of the request. This status code is recorded in the IIS log, and it may also be displayed in the Web browser or FTP client. The status code can indicate whether a particular request is successful or unsuccessful and can also reveal the exact reason why a request is unsuccessful. There are 5 groups ranging from 1xx - 5xx of http status codes exists.
101 - Switching protocols.
200 - OK. The client request has succeeded
302 - Object moved.
400 - Bad request.
500.13 - Web server is too busy.

31. Explain < @OutputCache% > and the usage of VaryByParam, VaryByHeader.
OutputCache is used to control the caching policies of an ASP.NET page or user control. To cache a page @OutputCache directive should be defined as follows < %@ OutputCache Duration="100" VaryByParam="none" % >

VaryByParam: A semicolon-separated list of strings used to vary the output cache. By default, these strings correspond to a query string value sent with GET method attributes, or a parameter sent using the POST method. When this attribute is set to multiple parameters, the output cache contains a different version of the requested document for each specified parameter. Possible values include none, *, and any valid query string or POST parameter name.

VaryByHeader: A semicolon-separated list of HTTP headers used to vary the output cache. When this attribute is set to multiple headers, the output cache contains a different version of the requested document for each specified header.

32. What is the difference between repeater over datalist and datagrid?

The Repeater class is not derived from the WebControl class, like the DataGrid and DataList. Therefore, the Repeater lacks the stylistic properties common to both the DataGrid and DataList. What this boils down to is that if you want to format the data displayed in the Repeater, you must do so in the HTML markup.
The Repeater control provides the maximum amount of flexibility over the HTML produced. Whereas the DataGrid wraps the DataSource contents in an HTML < table >, and the DataList wraps the contents in either an HTML < table > or < span > tags (depending on the DataList's RepeatLayout property), the Repeater adds absolutely no HTML content other than what you explicitly specify in the templates.
While using Repeater control, If we wanted to display the employee names in a bold font we'd have to alter the "ItemTemplate" to include an HTML bold tag, Whereas with the DataGrid or DataList, we could have made the text appear in a bold font by setting the control's ItemStyle-Font-Bold property to True.
The Repeater's lack of stylistic properties can drastically add to the development time metric. For example, imagine that you decide to use the Repeater to display data that needs to be bold, centered, and displayed in a particular font-face with a particular background color. While all this can be specified using a few HTML tags, these tags will quickly clutter the Repeater's templates. Such clutter makes it much harder to change the look at a later date. Along with its increased development time, the Repeater also lacks any built-in functionality to assist in supporting paging, editing, or editing of data. Due to this lack of feature-support, the Repeater scores poorly on the usability scale.

However, The Repeater's performance is slightly better than that of the DataList's, and is more noticeably better than that of the DataGrid's. Following figure shows the number of requests per second the Repeater could handle versus the DataGrid and DataList

33. Can we handle the error and redirect to some pages using web.config?

Yes, we can do this, but to handle errors, we must know the error codes; only then we can take the user to a proper error message page, else it may confuse the user.
CustomErrors Configuration section in web.config file:
The default configuration is:
< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
  < error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
If mode is set to Off, custom error messages will be disabled. Users will receive detailed exception error messages.
If mode is set to On, custom error messages will be enabled.
If mode is set to RemoteOnly, then users will receive custom errors, but users accessing the site locally will receive detailed error messages.
Add an < error > tag for each error you want to handle. The error tag will redirect the user to the Notfound.aspx page when the site returns the 404 (Page not found) error.


[Example]

There is a page MainForm.aspx

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Put user code to initialize the page here
Dim str As System.Text.StringBuilder
str.Append("hi") ' Error Line as str is not instantiated
Response.Write(str.ToString)
End Sub

[Web.Config]

< customErrors mode="On" defaultRedirect="Error.aspx"/ >
' a simple redirect will take the user to Error.aspx [user defined] error file.

< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
  < error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
'This will take the user to NotFound.aspx defined in IIS.

34. How do you implement Paging in .Net?

The DataGrid provides the means to display a group of records from the data source (for example, the first 10), and then navigate to the "page" containing the next 10 records, and so on through the data.

Using Ado.Net we can explicit control over the number of records returned from the data source, as well as how much data is to be cached locally in the DataSet.
1.Using DataAdapter.fill method give the value of 'Maxrecords' parameter
(Note: - Don't use it because query will return all records but fill the dataset based on value of 'maxrecords' parameter).
2.For SQL server database, combines a WHERE clause and a ORDER BY clause with TOP predicate.
3.If Data does not change often just cache records locally in DataSet and just take some records from the DataSet to display.

35. Can you create an app domain?

Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class
1. Public static AppDomain CreateDomain(String friendlyName)
2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)

36. Explain the differences between Server-side and Client-side code?

Server side code executes on the server.For this to occur page has to be submitted or posted back.Events fired by the controls are executed on the server.Client side code executes in the browser of the client without submitting the page.
e.g. In ASP.NET for webcontrols like asp:button the click event of the button is executed on the server hence the event handler for the same in a part of the code-behind (server-side code). Along the server-side code events one can also attach client side events which are executed in the clients browser i.e. javascript events.

37. How does VB.NET/C# achieve polymorphism?

Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class 'vehicle' is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.

C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.

Can you explain what inheritance is and an example of when you might use it?
The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.

        savingaccount s = new savingaccount ( "Amar", 5600.00f ) ;
From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member's name and balance are initialised.

We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class's methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.

Working of currentaccount class is more or less similar to that of savingaccount class.
Using the derived class's object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class's object we can call base class's methods, but the reverse is not allowed.

Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class.
Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.

        account a1 = new    savingaccount ( "Amar", 5600.00f ) ;
   account a2 = new currentaccount ( "MyCompany Pvt. Ltd.", 126000.00f) ;
Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.

        public virtual void display( )    {   }
We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.

        public override void display( )   {   }
Now it is ensured that when we call the methods using upcasted reference, it is the derived class's method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.

If we don't want to override base class's virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.

38. How would you implement inheritance using VB.NET/C#?

When we set out to implement a class using inheritance, we must first start with an existing class from which we will derive our new subclass. This existing class, or base class, may be part of the .NET system class library framework, it may be part of some other application or .NET assembly, or we may create it as part of our existing application. Once we have a base class, we can then implement one or more subclasses based on that base class. Each of our subclasses will automatically have all of the methods, properties, and events of that base class ? including the implementation behind each method, property, and event. Our subclass can add new methods, properties, and events of its own - extending the original interface with new functionality. Additionally, a subclass can replace the methods and properties of the base class with its own new
implementation - effectively overriding the original behavior and replacing it with new behaviors. Essentially inheritance is a way of merging functionality from an existing class into our new subclass. Inheritance also defines rules for how these methods, properties, and events can be merged. In VB.NET we can use implements keyword for inheritance, while in C# we can use the sign ( : ) between subclass and baseclass.

39. How is a property designated as read-only?

In VB.NET:

Private mPropertyName as DataType
Public ReadOnly Property PropertyName() As DataType
    Get Return mPropertyName
    End Get
End Property

In C#

Private DataType mPropertyName;
public returntype PropertyName
{
      get{
                        //property implementation goes here
                        return mPropertyName;
            }
            // Do not write the set implementation
}

 


40 .What is hiding in CSharp ?

Hiding is also called as Shadowing. This is the concept of Overriding the methods. It is a concept used in the Object Oriented Programming.

E.g.
 public class ClassA {
 public virtual void MethodA() {
  Trace.WriteLine("ClassA Method");
 }
}

public class ClassB : ClassA {
 public new void MethodA() {
  Trace.WriteLine("SubClass ClassB Method");
 }
}

public class TopLevel {
 static void Main(string[] args) {
  TextWriter tw = Console.Out;
  Trace.Listeners.Add(new TextWriterTraceListener(tw));
 
  ClassA obj = new ClassB();
  obj.MethodA(); // Outputs "Class A Method"
 
  ClassB obj1 = new ClassB();
  obj.MethodA(); // Outputs "SubClass ClassB Method"
 }
}

41. What is the difference between an XML "Fragment" and an XML "Document."
An XML fragment is an XML document with no single top-level root element. To put it simple it is a part (fragment) of a well-formed xml document. (node) Where as a well-formed xml document must have only one root element.

42. What does it meant to say "the canonical" form of XML?

"The purpose of Canonical XML is to define a standard format for an XML document. Canonical XML is a very strict XML syntax, which lets documents in canonical XML be compared directly.
Using this strict syntax makes it easier to see whether two XML documents are the same. For example, a section of text in one document might read Black & White, whereas the same section of text might read Black & White in another document, and even in another. If you compare those three documents byte by byte, they'll be different. But if you write them all in canonical XML, which specifies every aspect of the syntax you can use, these three documents would all have the same version of this text (which would be Black & White) and could be compared without problem.
This Comparison is especially critical when xml documents are digitally signed. The digital signal may be interpreted in different way and the document may be rejected.

43. Why is the XML InfoSet specification different from the Xml DOM? What does the InfoSet attempt to solve?

"The XML Information Set (Infoset) defines a data model for XML. The Infoset describes the abstract representation of an XML Document. Infoset is the generalized representation of the XML Document, which is primarily meant to act as a set of definitions used by XML technologies to formally describe what parts of an XML document they operate upon.
The Document Object Model (DOM) is one technology for representing an XML Document in memory and to programmatically read, modify and manipulate a xml document.
Infoset helps defining generalized standards on how to use XML that is not dependent or tied to a particular XML specification or API. The Infoset tells us what part of XML Document should be considered as significant information.

44. Contrast DTDs versus XSDs. What are their similarities and differences? Which is preferred and why?

Document Type Definition (DTD) describes a model or set of rules for an XML document. XML Schema Definition (XSD) also describes the structure of an XML document but XSDs are much more powerful.
The disadvantage with the Document Type Definition is it doesn't support data types beyond the basic 10 primitive types. It cannot properly define the type of data contained by the tag.
An Xml Schema provides an Object Oriented approach to defining the format of an xml document. The Xml schema support most basic programming types like integer, byte, string, float etc., We can also define complex types of our own which can be used to define a xml document.
Xml Schemas are always preferred over DTDs as a document can be more precisely defined using the XML Schemas because of its rich support for data representation.

45. Speaking of Boolean data types, what's different between C# and C/C++?
There's no conversion between 0 and false, as well as any other number and true, like in C/C++.

46. How do you convert a string into an integer in .NET?
Int32.Parse(string)

47. Can you declare a C++ type destructor in C# like ~MyClass()? Yes, but what's the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up,  plus, it introduces additional load on the garbage collector.

48. What's different about namespace declaration when comparing that to package declaration in Java? No semicolon.

49. Can you change the value of a variable while debugging a C# application?

Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

50. What's the implicit name of the parameter that gets passed into the class' set method?

Value, and it's datatype depends on whatever variable we're changing.

51. How do you inherit from a class in C#?

Place a colon and then the name of the base class. Notice that it's double colon in C++.

52. Does C# support multiple inheritance?

No, use interfaces instead.

53. So how do you retrieve the customized properties of a .NET application from XML .config file? Can you automate this process?

Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable. In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.

54. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio?

The designer will likely through it away, most of the code inside InitializeComponent is auto-generated.

55. Where do you add an event handler?

It's the Attributesproperty, the Add function inside that property.
e.g. btnSubmit.Attributes.Add(""onMouseOver"",""someClientCode();"")

56. What are jagged array?

First lets us answer the question that what an array is?
The dictionary meaning of array is an orderly arrangement or sequential arrangement of elements.
In computer science term:
An array is a data structure that contains a number of variables, which are accessed through computed indices. The variables contained in an array, also called the elements of the array, are all of the same type, and this type is called the element type of the array.

An array has a rank that determines the number of indices associated with each array element. The rank of an array is also referred to as the dimensions of the array. An array with a rank of one is called a single-dimensional array. An array with a rank greater than one is called a multi-dimensional array. Specific sized multidimensional arrays are often referred to as two-dimensional arrays, three-dimensional arrays, and so on.

Now let us answer What are jagged arrays?
 A jagged array is an array whose elements are arrays. The elements of jagged array can be of different dimensions and sizes. A jagged array is sometimes called as "array-of-arrays". It is called jagged because each of its rows is of different size so the final or graphical representation is not a square.

 When you create a jagged array you declare the number of rows in your array. Each row will hold an array that will be on any length. Before filling the values in the inner arrays you must declare them.

Jagged array declaration in C#:

 For e.g. : int [] [] myJaggedArray = new int [3][];

Declaration of inner arrays:
 
 myJaggedArray[0] = new int[5] ;   // First inner array will be of length 5.
 myJaggedArray[1] = new int[4] ;  // Second inner array will be of length 4.
 myJaggedArray[2] = new int[3] ;   // Third inner array will be of length 3.

Now to access third element of second row we write:
  int value = myJaggedArray[1][2];

Note that while declaring the array the second dimension is not supplied because this you will declare later on in the code.

Jagged array are created out of single dimensional arrays so be careful while using them. Don't confuse it with multi-dimensional arrays because unlike them jagged arrays are not rectangular arrays.

For more information on arrays:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfarrayspg.asp 

57. What is a delegate, why should you use it and how do you call it ?

A delegate is a reference type that refers to a Shared method of a type or to an instance method of an object. Delegate is like a function pointer in C and C++.  Pointers are used to store the address of a thing. Delegate lets some other code call your function without needing to know where your function is actually located. All events in .NET actually use delegates in the background to wire up events. Events are really just a modified form of a delegate.
It should give you an idea of some different areas in which delegates may be appropriate:

  • They enable callback functionality in multi-tier applications as demonstrated in the examples above. <o:p></o:p>
  • The CacheItemRemoveCallback delegate can be used in ASP.NET to keep cached information up to date. When the cached information is removed for any reason, the associated callback is exercised and could contain a reload of the cached information. <o:p></o:p>
  • Use delegates to facilitate asynchronous processing for methods that do not offer asynchronous behavior.

Events use delegates so clients can give the application events to call when the event is fired. Exposing custom events w

 

58.  What is datagrid? The DataGrid Web server control is a powerful tool for displaying information from a data source. It is easy to use; you can display editable data in a professional-looking grid by setting only a few properties. At the same time, the grid has a sophisticated object model that provides you with great flexibility in how you display the data.

59.  What's the difference between the System.Web.UI.WebControls.DataGrid and and 59. System.Windows.Forms.DataGrid? The Web UI control does not inherently support master-detail data structures. As with other Web server controls, it does not support two-way data binding. If you want to update data, you must write code to do this yourself. You can only edit one row at a time. It does not inherently support sorting, although it raises events you can handle in order to sort the grid contents. You can bind the Web Forms DataGrid to any object that supports the IEnumerable interface. The Web Forms DataGrid control supports paging. It is easy to customize the appearance and layout of the Web Forms DataGrid control as compared to the Windows Forms one.

60. How do you customize the column content inside the datagrid? If you want to customize the content of a column, make the column a template column. Template columns work like item templates in the DataList or Repeater control, except that you are defining the layout of a column rather than a row.

62. How do you apply specific formatting to the data inside the cells? You cannot specify formatting for columns generated when the grid's AutoGenerateColumns property is set to true, only for bound or template columns. To format, set the column's DataFormatString property to a string-formatting expression suitable for the data type of the data you are formatting.

63.   How do you hide the columns? One way to have columns appear dynamically is to create them at design time, and then to hide or show them as needed. You can do this by setting a column's Visible property.

64. How do you display an editable drop-down list? Displaying a drop-down list requires a template column in the grid. Typically, the ItemTemplate contains a control such as a data-bound Label control to show the current value of a field in the record. You then add a drop-down list to the EditItemTemplate. In Visual Studio, you can add a template column in the Property builder for the grid, and then use standard template editing to remove the default TextBox control from the EditItemTemplate and drag a DropDownList control into it instead. Alternatively, you can add the template column in HTML view. After you have created the template column with the drop-down list in it, there are two tasks. The first is to populate the list. The second is to preselect the appropriate item in the list — for example, if a book's genre is set to "fiction," when the drop-down list displays, you often want "fiction" to be preselected.

65.   How do you check whether the row data has been changed? The definitive way to determine whether a row has been dirtied is to handle the changed event for the controls in a row. For example, if your grid row contains a TextBox control, you can respond to the control's TextChanged event. Similarly, for check boxes, you can respond to a CheckedChanged event. In the handler for these events, you maintain a list of the rows to be updated. Generally, the best strategy is to track the primary keys of the affected rows. For example, you can maintain an ArrayList object that contains the primary keys of the rows to update.

 

Frequently Asked Questions

Question: How do I use a "helper function" to alter the output within my Datagrid based on a value from the DataSource?

Answer: Here is a sample use of a helper function (VB.Net)

<asp:DataGrid id="YourID" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateColumn HeaderText="Status">
  <ItemTemplate>
    <%#ShowStatus(Container.DataItem("online"))%>
  </ItemTemplate>
</asp:TemplateColumn>

Function ShowStatus(val)
  If val = 0 Then
    ShowStatus = "Offline"
  Else
    ShowStatus = "Online"
  End If
End Function

Question: How do I change the width of the Textboxes created in edit-mode of my Datagrid?

Updated! Answer: Here's an example of how to set the width of an edit Textbox in the EditItemTemplate of your TemplateColumn:

<asp:DataGrid id="YourID" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateColumn HeaderText="Sample Column">
  <ItemTemplate>
    <%#Container.DataItem("AColumnName")%>
  </ItemTemplate>
  <EditItemTemplate>
    <asp:Textbox runat="server" width="600" maxlength="600"/>
  </EditItemTemplate>
</asp:TemplateColumn>

And for a BoundColumn, you can modify the width just before the Datagrid is rendered:

Private Sub DataGrid1_PreRender(s As Object, e As EventArgs)
If DataGrid1.EditItemIndex > -1 Then
  Dim tbx As TextBox
  tbx = CType(DataGrid1.Items(DataGrid1.EditItemIndex).Cells(0).Controls(0), TextBox)
  tbx.Width = Unit.Parse("1cm")
End If
End Sub

Question: How do I hide a column in my Datagrid if AutoGenerateColumns is set to True?

Answer: AutoGenerated columns do not appear in the Datagrid's Columns() collection, and so the usual method of hiding a Datagrid column will fail:

'Will NOT work for AutoGenerated columns:
Datagrid1.Columns(1).Visible = False

So the place to handle this is in the ItemDataBound event of the Datagrid:

<asp:DataGrid id="Datagrid1" runat="server" AutoGenerateColumns="True" OnItemDataBound="Datagrid1_OnItemDataBound"/>

Private Sub DataGrid1_ItemDataBound(s As Object, e As DatagridItemEventArgs)
  e.Item.Cells(1).Visible = False
End Sub

Question: When I try to do an Update from my Datagrid, I keep getting the old/original values. Why?

Answer: This is caused by calling DataBind() on the grid before retrieving the updated values. The DataBind() overwrites the updates with the original values. Usually caused by having the initial DataBind() of the grid called on every Page_Load. Solution: call DataBind() only the first time the page is loaded:

Sub Page_Load(s As Object, e As EventArgs)
  If Not IsPostBack Then BindGrid()
End Sub

Question: How do I conditionally set the backcolor of a cell in my Datagrid based on a value from the database? (conditional formatting)

Answer: Handle this in the ItemDataBound event, where you can access the DataItem as it is bound to the Datagrid, and the Cells() collection of the current Datagrid item.

Sub Datagrid1_ItemDataBound(source As Object, e As DataGridItemEventArgs)
  If (e.Item.ItemType = ListItemType.Item Or _
    e.Item.ItemType = ListItemType.AlternatingItem) Then
    If Convert.ToDateTime(e.Item.Cells(1).Text) < DateTime.Today Then _
    e.Item.Cells(1).BackColor = System.Drawing.Color.FromName("#ffccff")
    If e.Item.DataItem("UserID") = 590 Then _
    e.Item.Cells(2).BackColor = System.Drawing.Color.DeepPink
  End If
End Sub

Question: How do I specify more than one parameter for my HyperlinkColumn?

Answer: The HyperlinkColumn's DataNavigateUrlFormatString only supports one parameter. If you need more than one, switch to a TemplateColumn with an <asp:Hyperlink>.
Note: You should always encode values passed into querystring to protect against spaces and special characters.

<asp:DataGrid id="YourID" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateColumn HeaderText="Sample Column">
  <ItemTemplate>
    <asp:Hyperlink runat="server" Text='<%#Container.DataItem("TextVal")%>' NavigateUrl='<%# "page.aspx?Param1=" & Server.UrlEncode(Container.DataItem("Val1")) & "&Param2=" & Server.UrlEncode(Container.DataItem("Val2"))%>'/>
  </ItemTemplate>
</asp:TemplateColumn>
</Columns>

Question: How can I make the content of one of my Datagrid cells span more than one line? Or, how do I display more than one field of data in the same cell?

Answer: Use a TemplateColumn, and inside the ItemTemplate (or EditItemTemplate), you can use <br> tags or any other formatting you might want.

<asp:DataGrid id="YourID" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateColumn HeaderText="Sample Column">
  <ItemTemplate>
<%#Container.DataItem("Field1")%>
<br>
<%#Container.DataItem("Field2")%>
  </ItemTemplate>
</asp:TemplateColumn>
</Columns>

 

Remoting FAQ's

 

1.    What distributed process frameworks outside .NET do you know?
Distributed Computing Environment/Remote Procedure Calls (DEC/RPC), Microsoft Distributed Component Object Model  (DCOM), Common Object Request Broker Architecture (CORBA), and Java Remote Method Invocation (RMI).

2.    What are possible implementations of distributed applications in .NET?
 .NET Remoting and ASP.NET Web Services. If we talk about the Framework Class Library, noteworthy classes are in  System.Runtime.Remoting and System.Web.Services.

3.    When would you use .NET Remoting and when Web services?
Use remoting for more efficient exchange of information when you control both ends of the application. Use Web services for     open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else.

4.    What's a proxy of the server object in .NET Remoting?
 It's a fake copy of the server object that resides on the client side and behaves as if it was the server. It handles the  communication between real server object and the client object. This process is also known as marshaling.

5.    What are remotable objects in .NET Remoting?
Remotable objects are the objects that can be marshaled across the application domains. You can marshal by value, where  a deep copy of the object is created and then passed to the receiver. You can also marshal by reference, where just a  reference to an existing object is passed.

6.    What are channels in .NET Remoting?
Channels represent the objects that transfer the other serialized objects from one application domain to another and from  one computer to another, as well as one process to another on the same box. A channel must exist before an object can be transferred.

7.    What security measures exist for .NET Remoting in System.Runtime.Remoting?
 None. Security should be taken care of at the application level. Cryptography and other security techniques can be applied  at application or server level.

8.    What is a formatter?
 A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing  and decoding messages into data on the other end.

9.    Choosing between HTTP and TCP for protocols and Binary and SOAP for formatters, what are the trade-offs?
Binary over TCP is the most effiecient, SOAP over HTTP is the most interoperable.

10. What's SingleCall activation mode used for?
If the server object is instantiated for responding to just one single request, the request should be made in SingleCall mode.

11. What's Singleton activation mode?
A single object is instantiated regardless of the number of clients accessing it. Lifetime of this object is determined by  lifetime lease.

12. How do you define the lease of the object?
By implementing ILease interface when writing the class code.

13. Can you configure a .NET Remoting object via XML file?
Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config.

14. How can you automatically generate interface for the remotable object in .NET with Microsoft tools?
Use the Soapsuds tool.   

 

15. What are CAO's i.e. Client Activated Objects ?
Client-activated objects are objects whose lifetimes are controlled by the calling application domain, just as they would be if the object were local to the client. With client activation, a round trip to the server occurs when the client tries to create an instance of the server object, and the client proxy is created using an object reference (ObjRef) obtained on return from the creation of the remote object on the server. Each time a client creates an instance of a client-activated type, that instance will service only that particular reference in that particular client until its lease expires and its memory is recycled. If a calling application domain creates two new instances of the remote type, each of the client references will invoke only the particular instance in the server application domain from which the reference was returned.

In COM, clients hold an object in memory by holding a reference to it. When the last client releases its last reference, the object can delete itself. Client activation provides the same client control over the server object's lifetime, but without the complexity of maintaining references or the constant pinging to confirm the continued existence of the server or client. Instead, client-activated objects use lifetime leases to determine how long they should continue to exist. When a client creates a remote object, it can specify a default length of time that the object should exist. If the remote object reaches its default lifetime limit, it contacts the client to ask whether it should continue to exist, and if so, for how much longer. If the client is not currently available, a default time is also specified for how long the server object should wait while trying to contact the client before marking itself for garbage collection. The client might even request an indefinite default lifetime, effectively preventing the remote object from ever being recycled until the server application domain is torn down. The difference between this and a server-activated indefinite lifetime is that an indefinite server-activated object will serve all client requests for that type, whereas the client-activated instances serve only the client and the reference that was responsible for their creation. For more information, see Lifetime Leases.

To create an instance of a client-activated type, clients either configure their application programmatically (or using a configuration file) and call new (New in Visual Basic), or they pass the remote object's configuration in a call to Activator.CreateInstance. The following code example shows such a call, assuming a TcpChannel has been registered to listen on port 8080.

 

16. How many processes can listen on a single TCP/IP port?
One.

 

17. What technology enables out-of-proc communication in .NET?
Most usually Remoting;.NET remoting enables client applications to use objects in other processes on the same computer or on any other computer available on its network.While you could implement an out-of-proc component in any number of other ways, someone using the term almost always means Remoting.

 

18. How can objects in two diff. App Doimains communicate with each other?
.Net framework provides various ways to communicate with objects in different app domains.
First is XML Web Service on internet, its good method because it is built using HTTP protocol and SOAP formatting.
If the performance is the main concern then go for second option which is .Net remoting because it gives you the option of using binary encoding and the default TcpChannel, which offers the best interprocess communication performance

19. What is the difference between .Net Remoting and Web Services?

Although we can develop an application using both technologies, each of them has its distinct advantages. Yes you can look at them in terms of performance but you need to consider your need first. There are many other factors such authentications, authorizing in process that need to be considered.

 Point

 Remoting

 Webservices

 If your application needs interoperability with other platforms or operating systems

 No

 Yes, Choose Web Services because it is more flexible in that they are support SOAP.

 If performance is the main requirement with security

 You should use the TCP channel and the binary formatter

 No

 Complex Programming

 Yes

 No

 State Management

 Supports a range of state management, depending on what object lifetime scheme you choose (single call or singleton call).

 Its stateless service management (does not inherently correlate multiple calls from the same user) 

 Transport Protocol

 It can access through TCP or HTTP channel.

 It can be access only through HTTP channel.

 

WinForms FAQ :


1.    What base class do all Web Forms inherit from?
System.Windows.Forms.Form

 

2.    What is the difference between Debug.Write and Trace.Write? When should each be used?
The Debug.Write call won't be compiled when the DEBUGsymbol is not defined (when doing a release build). Trace.Write calls will be compiled. Debug.Write is for information you want only in debug builds, Trace.Write is for when you want it in release build as well.

 

3.    Difference between Anchor and Dock Properties?

Dock Property->Gets or sets which edge of the parent container a control is docked to. A control can be docked to one edge of its parent container or can be docked to all edges and fill the parent container. For example, if you set this property to DockStyle.Left, the left edge of the
control will be docked to the left edge of its parent control. Additionally, the docked edge of  the control is resized to match that of its container
control.
Anchor Property->Gets or sets which edges of the control are anchored to the edges of its container.  A control can be anchored to one or more edges of its parent container. Anchoring a control to its parent ensures that the anchored edges remain in the same position relative to the edges of the parent container when the parent container is resized.

 

4.    When would you use ErrorProvider control?
ErrorProvider control is used in Windows Forms application. It is like Validation Control for ASP.NET pages. ErrorProvider control is used to provide validations in Windows forms and display user friendly messages to the user if the validation fails.
 E.g
 If we went to validate the textBox1 should be empty, then we can validate as below
 1). You need to place the errorprovide control on the form
 private void textBox1_Validating(object sender, System.ComponentModel.CancelEventArgs e)
{
ValidateName();
}

private bool ValidateName()
{
bool bStatus = true;
if (textBox1.Text == "")
{
errorProvider1.SetError (textBox1,"Please enter your Name");
bStatus = false;
}
else
errorProvider1.SetError (textBox1,"");
return bStatus;
}

 it check the textBox1 is empty . If it is empty, then a message Please enter your name is displayed.

 

5.    Can you write a class without specifying namespace? Which namespace does it belong to by default??
Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you  wouldn't want global namespace.

 

6.    You are designing a GUI application with a windows and several widgets on it. The user then resizes the app window and sees a lot of grey space, while the widgets stay in place. What's the problem? 
One should use anchoring for correct resizing. Otherwise the default property of a widget on a form is top-left, so it stays at  the same location when resized.

 

7.    How can you save the desired properties of Windows Forms application? 
.config files in .NET are supported through the API to allow storing and retrieving information. They are nothing more than simple XML files, sort of like what .ini files were before for Win32 apps.

 

8.    So how do you retrieve the customized properties of a .NET application from XML .config file? 
Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable.

 

9.    Can you automate this process? 
In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.

 

10. My progress bar freezes up and dialog window shows blank, when an intensive background process takes over. 
Yes, you should've multi-threaded your GUI, with taskbar and main form being one thread, and the background process being the other.

 

11. What's the safest way to deploy a Windows Forms app?
Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges.

 

12. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio? 
The designer will likely through it away, most of the code inside InitializeComponent is auto-generated.

 

13. What's the difference between WindowsDefaultLocation and WindowsDefaultBounds?
WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS.

 

14. What's the difference between Move and LocationChanged? Resize and SizeChanged? 
Both methods do the same, Move and Resize are the names adopted from VB to ease migration to C#.

 

15. How would you create a non-rectangular window, let's say an ellipse? 
Create a rectangular form, set the TransparencyKey property to the same value as BackColor, which will effectively make the background of the form transparent. Then set the FormBorderStyle to FormBorderStyle.None, which will remove the contour and contents of the form.

 

16. How do you create a separator in the Menu Designer? 
A hyphen '-' would do it. Also, an ampersand '&\' would underline the next letter.

 

17. How's anchoring different from docking? 
Anchoring treats the component as having the absolute size and adjusts its location relative to the parent form. Docking  treats the component location as absolute and disregards the component size. So if a status bar must always be at the bottom no matter what, use docking. If a button should be on the top right, but change its position with the form being resized, use anchoring.

 

18. How do you trigger the Paint event in System.Drawing?
Invalidate the current form, the OS will take care of repainting. The Update method forces the repaint.

 

19. With these events, why wouldn't Microsoft combine Invalidate and Paint, so that you wouldn't have to tell it to repaint, and then to force it to repaint?
Painting is the slowest thing the OS does, so usually telling it to repaint, but not forcing it allows for the process to take place in the background.

 

20. How can you assign an RGB color to a System.Drawing.Color object?
Call the static method FromArgb of this class and pass it the RGB values.

 

21. What class does Icon derive from? 
Isn't it just a Bitmap with a wrapper name around it? No, Icon lives in System.Drawing namespace. It's not a Bitmap by default, and is treated separately by .NET. However, you can use ToBitmap method to get a valid Bitmap object from a valid Icon object.

 

22. Before in my VB app I would just load the icons from DLL. How can I load the icons provided by .NET dynamically? 
By using System.Drawing.SystemIcons class, for example System.Drawing.SystemIcons.Warning produces an Icon with a  warning sign in it.

 

23. When displaying fonts, what's the difference between pixels, points and ems? 
A pixel is the lowest-resolution dot the computer monitor supports. Its size depends on user's settings and monitor size. A point is always 1/72 of an inch. An em is the number of pixels that it takes to display the letter M.

 

24. What is a CLR host?

The Windows operating system does not provide support for running a CLR application. That support is provided by a CLR host. A CLR host is an application that is responsible for loading the CLR into a process, creating application domains within the process, and executing user code within the application domains. Examples of hosts that ship with the .NET Framework include:

ASP.NET. An ISAPI filter that ships with ASP.NET loads the CLR and does the initialization necessary to handle web requests.

Internet Explorer. A MIME filter hooks into Internet Explorer versions 5.01 and higher to execute managed controls referenced from HTML pages.

 Shell Executables. When a managed application is launched from a shell, a small piece of unmanaged code loads the CLR and transitions control of the application to the CLR.

 

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