jQuery-AJAX calling ASP.NET page method. How to return value back to jQuery?

Question

If I use jQuery AJAX to call a specific ASP.NET page method how to have that method return a value back to the AJAX method that called it?

Update

Answer 1

With pure ASP.NET (not talking WCF here) I'd go with a handler (ASHX) file, and use JSON as the interchange format. I won't get into the details of JSON (here is a decent start), but the idea is a lightweight handler on the server that generates json text and returns it to the client, which can then use the structure easily in javascript.

This is obviously a simplified example but the gist is the JSON can be data driven from the server and easily consumed by the javascript on the client.

server:

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;

public class Handler : IHttpHandler {

    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/json";
        context.Response.WriteFile("~/myData.json");
    }

    public bool IsReusable {
        get {
            return false;
        }
    }
}

client:

myData = 
      (function () 
       {
          var json = null;
          $.ajax({
              'async': false,
              'global': false,
              'url': "handler.ashx",
              'dataType': "json",
              'success': function (data) {    
                  // this code is called when the 
                  // data is returned from the server              
                  json = data;
              }
          });
          return json;    
      }
          )(); 

alert(myData.MyArray[0].MyProperty);