/************BEGIN - Client side code*****************/

$(document).ready(function(){
    $('#btnSubmit').click(function(){

// Below is an AJAX call which is throwing error.      

//        $.ajax({
//            type: "POST",
//            url: "CTypesHandler.ashx",
//            data: "{'fname':'"+$('#txtFirstName').val()+"'}",
//            contentType: "application/json; charset=utf-8",
//            dataType: "json",
//            success:function(msg){
//                alert(msg.fname);
//            },
//            error:function(xhr, status, errorThrown){
//                alert('Error'+errorThrown);
//            }
//        });


//Below is similar AJAX call as above using $.POST and it works!
      
  $.post("CTypesHandler.ashx", { fname : $('#txtFirstName').val()},fnCallback,"json");
        
            function fnCallback(response)
            {
                alert(response.fname);
            }
    });
});
/************END - Client side code*****************/


/************BEGIN - Server side code*****************/

<%@ WebHandler Language="VB" Class="CTypesHandler" %>

Imports System
Imports System.Web
Imports Jayrock.Json

Public Class CTypesHandler : Implements IHttpHandler
    
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
        Dim jsObj As New JsonObject
        Dim fname As String = ""
        Try
            fname = context.Request.Form("fname")
            jsObj("fname") = fname
            context.Response.ContentType = "application/json"
            context.Response.Write(jsObj)
        Catch ex As Exception
            context.Response.Write("hError")
        End Try
        
    End Sub
 
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return False
        End Get
    End Property

End Class

/************END - Server side code*****************/