Client Callbacks in ASP.NET 2.0

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page, ICallbackEventHandler   
{
    string callbackResult;
protected void Page_Load(object sender, EventArgs e)
{
    string cbref = Page.ClientScript.GetCallbackEventReference(this, "arg", "JSCallback", "context");
    //Response.Write(cbref);
    string cbScr = string.Format("function UseCallBack(arg, context) {{ {0}; }} ", cbref);
  //  Response.Write("<BR>" + cbScr);

    Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "UseCallBack", cbScr, true);
}

    #region ICallbackEventHandler Members

    public string GetCallbackResult()
    {
        return callbackResult;
    }

    public void RaiseCallbackEvent(string eventArgument)
    {
        // perform some real operation
        callbackResult = "DotNET Rocks!";
    }

    #endregion

}