ICallbackEventHandler in asp.net

//Code

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

public   partial   class  _Default : System.Web.UI.Page,ICallbackEventHandler
{
     public   string  results  =   string .Empty;
     protected   void  Page_Load( object  sender, EventArgs e)
    {
         string  strScript  =   string .Format( @" function ServerRequest(arg,ctx) {{ {0}; }}
" , Page.ClientScript.GetCallbackEventReference( this ,  " arg " ,  " GetResult " ,  " ctx " ,  " GetError " ,  false ));

        Page.ClientScript.RegisterClientScriptBlock( this .GetType(),  " CallbackFunctions " , strScript,  true );

    }

     #region  ICallbackEventHandler Members

     public   string  GetCallbackResult()
    {
         return  results;
    }

     public   void  RaiseCallbackEvent( string  eventArgument)
    {
        results  =   " false " ;
    }

     #endregion
     protected   void  Button1_Click( object  sender, EventArgs e)
    {
        Response.Write( " hello " );
    }
}

//Form

< html >
< head  runat ="server" >
     < title > Untitled Page </ title >
     < script  type ="text/javascript" >
       var  Mark = false ;
       function  CheckJsValidate()
      {
          if (Page_Validators[ 0 ].isvalid)
         {
            document.getElementById( " DivSecurity " ).style.display = " block " ;
         }
          else {
            document.getElementById( " DivSecurity " ).style.display = " none " ;
            }
      }
       // Check if the user answered his question correctly
       function  CheckAnquestion()
      { 
          var  varDrop  =  document.getElementById( " DropDownList1 " ).value;
          var  varTxt  =  document.getElementById( " TextBox3 " ).value;
        
         ServerRequest([varDrop,varTxt], "" )
          return   false ;
      }
       // If success,Submit the current form
       function  GetResult(result, context) {
          if (eval(result))
         {
            document.getElementById( " Button1 " ).click();
         } else
           alert( ' Your answer is wrong! ' )
      }
       // If false,alert the error message
       function  GetError(result, context) {
         alert(result);
      }
     </ script >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
    
         < asp:TextBox  ID ="TextBox1"  runat ="server"  TextMode ="Password" ></ asp:TextBox >
         < br  />
         < asp:TextBox  ID ="TextBox2"  runat ="server"  TextMode ="Password"  onblur ="CheckJsValidate()" ></ asp:TextBox >
         < br  />
         < asp:CompareValidator  ID ="CompareValidator1"  runat ="server"
         ControlToValidate ="TextBox1"  ControlToCompare ="TextBox2"  
         ErrorMessage ="CompareValidator" ></ asp:CompareValidator >
          < div  id ="DivSecurity"  style ="display:none" >
         < asp:DropDownList  ID ="DropDownList1"  runat ="server" >
         < asp:ListItem  Value ="Question1" > Question1 </ asp:ListItem >
         < asp:ListItem  Value ="Question2" > Question2 </ asp:ListItem >
         </ asp:DropDownList >
         < asp:TextBox  ID ="TextBox3"  runat ="server"   ></ asp:TextBox >
         < div  id ="DivResult" ></ div >
         </ div >
         < asp:Button  ID ="Button1"  runat ="server"  Text ="Submit"  
            OnClientClick ="javascript:return CheckAnquestion();"  onclick ="Button1_Click"   />
    
     </ div >
     </ form >
</ body >
</ html >