Creating JSON-enabled WCF services in

This is worth a look. Creating JSON-enabled WCF services in .NET 3.5 – an even simpler approach

setting Factory="System.ServiceModel.Activation.WebScriptServiceHostFactory" in your .svc file

I've done this in Framework 4.0 and it's supported there too.

ASP.NET AJAX Toolkit

http://www.asp.net/ajaxlibrary/download.ashx

AJAX call to ASMX usng JQuery with error handling

Here's the javascript

        function DoAjaxTest(str) {
            $.ajax({
                type: "POST",
                url: "Service1.asmx/TestMethod",
                data: "{'parameter1': '" + str +"'}",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (msg) {
                   alert(msg.d);
                },
                error: function (xhr, textStatus, errorThrown) {
                    //debugger;

                    var errObj={Message:'',ExceptionType:'',StackTrace:''};
                    //debugger;
                    if (xhr.status===500) {
                        //a thrown exception will have status 500.  the properties of Message,ExceptionType, StackTrace 
                        errObj = eval('(' + xhr.responseText + ')');
                    }
                    alert(
                        "Status: " + textStatus +
                        "; textStatus: " + textStatus +
                        "; reror Thrown: " + errorThrown +
                        "; status statusText: " + xhr.status + " " + xhr.statusText +
                        "; Error Message: " + errObj.Message +
                        "; 
stack trace:
 " + errObj.StackTrace.replace(/\n/g, "
\n") + "
" +
                        //"; xhr.responseText: " + xhr.responseText + 
                        "
");

                }
            });
        };

        $(document).ready(function () {
           
             DoAjaxTest('hello world');

        });

Here's the content of the Service1.asmx file:

<%@ WebService Language="C#" Class="testService" %>

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
// [System.Web.Script.Services.ScriptService]
public class testService  : System.Web.Services.WebService {

    [WebMethod]
    public string TestMethod(string parameter1)
    {
        
        return (DateTime.Now.ToLongTimeString() + ": " + parameter1);
    }
}

Microsoft ASP.NET: Taking AJAX to the Next Level

Hear how ASP.NET AJAX 4.0 makes building pure client-side AJAX Web applications even easier, and watch us build an entire data-driven ASP.NET AJAX application from start to finish by taking advantage of only JavaScript, HTML pages, and Windows Communication Foundation (WCF) services. Also learn about new ASP.NET AJAX features including the DataView control, declarative templates, live client-side data binding, WCF, and REST integration.
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