I am attempting to implement the ASP.NET 2.0's client callback feature.   My client side script looks similar to the following so far:

 function PrimeKeyCheck(sender, args)
 {
        var numberOfRecords=0;
        var hiddenField = document.getElementById("<%=NumOfRecordsHiddenField.ClientID%>");
   
        numberOfRecords = parseInt(hiddenField.value);
         if (numberOfRecords > 0)
        {
             args.IsValid = false;
            return;
        }

    args.IsValid = true;
    return;

    return ;
  }

The server side function that I need to call is SalesmanManagerBLL.GetCountARNumber(). This function will access a database to retrieve the record count from a particular table. The problem I am having is that I don't know how to properly implement the ICallbackEventHandler and Page.GetCallbackEventReference for client callback. I have read through the article ASP.NET 2.0's Client Callback Feature, but I am still a little confused. Any suggestions?

Here is simple way of doing client callback

on code behind side

public string callbackArg;

if (!IsPostBack)

So I what function would I call inside my script to get the result from  SalesmanManagerBLL.GetCountARNumber()? 

I dont know how u r trying to implement this. But my guess would be

function PrimeKeyCheck()
 {

      var context; // dont worry about this right now, you need consider only event arg

       callServer(10 , context);
  }

// In handle response from the server do  what ever u want;

function HandleResponse(eventarg , context)
{

 var numberofRecords = parseInt(eventarg);

// do what ever you want with this integer value;

}

 I am getting the following after implementing the suggested changes:

Looks like u didnt implemented ICallbackEventHandler interface. Your class should look like this

public partial class ManageUsers : System.Web.UI.Page, ICallbackEventHandler

{

public string callbackArg;

{

}