Step 1 -
   Create a reference to the ajax.dll file

Step 2 - Set up the HttpHandler
In the web.config, set up the HttpHandler, like:

<configuration>
  <system.web>
    <httpHandlers>
    <add verb="POST,GET" path="ajax/*.ashx" type="Ajax.PageHandlerFactory, Ajax" />
    </httpHandlers> 
    ...
  <system.web>
</configuration>

Step 3 -
In the Page_Load event, call the following function:

'vb.net
Public Class Index
  Inherits System.Web.UI.Page

  Private Sub Page_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Ajax.Utility.RegisterTypeForAjax(GetType(Index))
  '...
  end sub
  '...
End Class

//C#
public class Index : System.Web.UI.Page{
   private void Page_Load(object sender, EventArgs e){
      Ajax.Utility.RegisterTypeForAjax(typeof(Index));     
      //...
   }
   //... 
}

Step 4 -
In the codebehind of your page, add functions (like you normally would) that you'd like to be able to asynchrounsly called by client-side scripting.  Mark these functions with the Ajax.JavascriptMethodAttribute():

//C#
[Ajax.AjaxMethod()]
public int ServerSideAdd(int firstNumber, int secondNumber)
{
return firstNumber + secondNumber;
}

'VB.Net
<Ajax.AjaxMethod()> _
Public Function ServerSideAdd(ByVal firstNumber As Integer, ByVal secondNumber As Integer) As Integer
 Return firstNumber + secondNumber
End Function

The wrapper will automatically create a JavaScript function named "ServerSideAdd" which accepts to parameters.  When called, this server-side function will be called and the result returned.

Step 5 -
Using JavaScript, you can invote the ServerSideAdd function like you would any other JavaScript function.  You can call it using the two parameters, or optionally pass a call back function.  The name of the function is, by default, <name of class>.<name of server side function>, such as Index.ServerSideAdd:

alertIndex.ServerSideAdd(100,99));

OR

Index.ServerSideAdd(100,99, ServerSideAdd_CallBack);

function ServerSideAdd_CallBack(response){
 alert(response.value);
}

The response exposes three properties, error, value and request.

Note that you can return more complex objects that simple types.

See the demo for additional information:
http://ajax.schwarz-interactive.de/csharpsample/default.aspx

自己模仿它做出了第一个范例,希望更多人参与讨论