Using JQuery and JSON to consume Asp.net Server-Side Asynchronous Web Methods

Question

I defined two webservices calls in ASP.NET: 1.BeginLengthyProcedure and EndLengthyProcedure (Asynchronous web method) 2.LengthProcedureSync

namespace ServiceDemo
{
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
[System.Web.Script.Services.ScriptService]
public class AsyncWebService : System.Web.Services.WebService
{
    public delegate string LengthyProcedureAsyncStub(int milliseconds);

    public string LengthyProcedure(int milliseconds)
    {
        System.Threading.Thread.Sleep(milliseconds);
        return "SuccessAsync";
    }

    public class MyState
    {
        public object previousState;
        public LengthyProcedureAsyncStub asyncStub;
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public IAsyncResult BeginLengthyProcedure(int milliseconds, AsyncCallback cb, object s)
    {
        LengthyProcedureAsyncStub stub = new LengthyProcedureAsyncStub(LengthyProcedure);
        MyState ms = new MyState();
        ms.previousState = s;
        ms.asyncStub = stub;
        return stub.BeginInvoke(milliseconds, cb, ms);
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string EndLengthyProcedure(IAsyncResult call)
    {
        MyState ms = (MyState)call.AsyncState;
        string res = ms.asyncStub.EndInvoke(call);
        return res;
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string LengthyProcedureSync(int milliseconds)
    {
        System.Threading.Thread.Sleep(milliseconds);
        return "SuccessSync";
    }
}
}

Then I consumed them using JQuery, I don't want to use ASP.NET AJAX. LengthProcedureSync worked fine, but LenghtyProcudure didn't work. Is there anything I missed?

<script type="text/javascript" src="jquery-1.4.4.min.js"></script>

<script type="text/javascript">
    function testJson() {
        $.ajax({
            type: "POST",
            //Didn't work
            url: "AsyncWebService.asmx/LengthyProcedure",
            //Work
            //url: "AsyncWebService.asmx/LengthyProcedureSync",
            data: "{'milliseconds':'2000'}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (msg) {
                $("#jsonResponse").html(msg.d);
            },
            error: function (msg) {

            }

        });
    };

</script>

Were you able to call BeginLengthyProcedure from jQuery and get results from EndLengthyProcedure? How? — Tony_Henrich
– Tony_Henrich, Commented Apr 7, 2011 at 1:34

Hans · Accepted Answer · 2011-08-13 13:37:04Z

1

Unfortunately, the .NET Framework's ASP.NET AJAX web service handler (which is used for JSON) does not provide support for asynchronous web service calls whereas the default ASP.NET web service handler does. There is an excellent book "Building a Web 2.0 Portal with ASP.NET 3.5" written by Omar AL Zabir describing a workaround for this shortcoming of the ASP.NET AJAX web service handler (see chapter 7, page 177). There is also a sample chapter available on MSDN. Hope, this helps!

answered Aug 13, 2011 at 13:37

Hans

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1 Comment

Lukáš Lánský Over a year ago

That's terrible. I hate my job.

Mark Schultheiss · Accepted Answer · 2011-01-27 14:45:51Z

0

change this

public string LengthyProcedure(int milliseconds)
     {
         System.Threading.Thread.Sleep(milliseconds);
         return "SuccessAsync";
     }

to this:

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public string LengthyProcedure(int milliseconds)
     {
           System.Threading.Thread.Sleep(milliseconds);         
           return "SuccessAsync";
     }

answered Jan 27, 2011 at 14:45

Mark Schultheiss

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4 Comments

YuQing Zhang Over a year ago

Then I think the client side would call this synchronous web method directly instead of calling the asynchronous web method.

Mark Schultheiss Over a year ago

I think you miss the point, without the decoration, the method will not be exposed as a web method and thus your call to it via url: "AsyncWebService.asmx/LengthyProcedure", is invalid.

Mark Schultheiss Over a year ago

Note as here: api.jquery.com/jQuery.ajax async: defaults to true, but can be set to false if you desire it to be called synchronous

YuQing Zhang Over a year ago

No, "AsyncWebService.asmx/LengthyProcedure" is valid, it is just an implementation detail, called asynchronous design pattern in .NET. With Begin*** and End*** webmethods, the * method will look and behave exactly as synchronous method. Maybe it is a little bit confusing to use LenghtyProcedure for the first non-webmethod function.

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