Friday, October 30, 2009

Posting form data from <a href="http://ASP.NET">ASP.NET</a> page to another URL


Sometime you need to post a form to an different url from pages, for example you might need to send user to third party payment processing system using post method, does not provide any straight forward way to accomplish this task.

Problem which most users faces with server side form in aspx page are, you are not allowed to change action of form and you are allowed to use only one server side form per page.

Possible Solutions.

1. One possible solution to this problem is to Create your own form control and use it on page this will allow you to change action of form, but again what if you do not want some existing input elements in current page to go to post.

2. There is good way to post form data using HttpWebResponse & HttpWebRequest class if you want to post data behind the scenes, but if you want to post data using user browser then you are stuck.

Our Solution.

I will try to show you one possible way to accomplish this task, we will create 1)component that will create form with required fields and post the form to specified url, 2) web page that will use that component to post data and 3) page which will receive that data and display posted data.

A) RemotePost Class.

Public Class RemotePost
Private Inputs As System.Collections.Specialized.NameValueCollection = New System.Collections.Specialized.NameValueCollection

Public Url As String = ""
Public Method As String = "post"
Public FormName As String = "form1"
Public Sub Add(ByVal name As String, ByVal value As String)
Inputs.Add(name, value)
End Sub
Public Sub Post()
System.Web.HttpContext.Current.Response.Clear()System.Web.HttpContext.Current.Response.Write("")System.Web.HttpContext.Current.Response.Write(String.Format("", FormName))System.Web.HttpContext.Current.Response.Write(String.Format("", FormName, Method, Url))
Dim i As Integer = 0
Do While i < Inputs.Keys.Count
System.Web.HttpContext.Current.Response.Write(String.Format("", Inputs.Keys(i), Inputs(Inputs.Keys(i))))
i += 1
End Sub
End Class

Properties of our component.

1. "Url" which is action of our form.
2. "Method" which is Method of our form, default is Post but you can also use Get.
3. "FormName" which is name of form.

Methods of our component.

1. "Add" which will be used to add form input name and value. and

2. "Post" which will render html on page to do actual posting, most important part of this method is onload event of rendered html's body which will post form to specified URL.

3. Private field Inputs which will hold name value pair collection of all inputs that goes into form.

4. You can compile this class to dll and use in your project but for simplicity I am including that class directly into page itself.

B) Sample Page.

Following is sample page code which posts form to specified url.

Dim myremotepost As RemotePost = New RemotePost
myremotepost.Url = htttp://"myremotepost.Add("field1", "Huckleberry")
myremotepost.Add("field2", "Finn")

C) Receiving Page.

Following is sample page code which posts form to specified url.

This is the page where posting will occur for simplicity we will just write posed value so that we can know what was posted.

If Not Request.Form("field1") Is Nothing Then
Response.Write("field1 : " & Request.Form("field1") & "")
End If
If Not Request.Form("field2") Is Nothing Then
Response.Write("field2 : " & Request.Form("field2") & "")
End If

Run Sample

Click "" target="new">here to run sample

There will be cases where you will need to tweak the code to suit your requirement. you will also need to check scenario where user uses back button of browser(from posted p
in reference to:
"Posting form data from ASP.NET page to another URL"
- Posting form data from ASP.NET page to another URL (view on Google Sidewiki)

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