How to: JSONify ASP.NET Webservice (ASP.NET 2.0) + DOJO + AJAX

Question:
How do I return JSON-formatted data from ASP.NET service? Found the article (please see reference); however, it's returning XML instead of JSON.
Please help.
Steve ho
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Reference: http://blog.davebouwman.net/2008/06/10/AccessingASPNETWebServicesWithDojoxhrGet.aspx
Output:
<?xml version="1.0" encoding="utf-8"?><string xmlns="http://microsoft.com/webservices/">Hello World</string>  === cmsWS.asmx.cs ===
 using System;
using System.Data;
using System.Web;
using System.Collections;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.ComponentModel;
using System.Web.Script.Services;
namespace WSLCBWS
{
    /// <summary>
    // ...