Question

Possible Duplicate:
How do I return the response from an asynchronous call?

I am using Jquery Ajax to call a service to update a value.

function ChangePurpose(Vid, PurId) {
    var Success = false;
    $.ajax({
        type: "POST",
        url: "CHService.asmx/SavePurpose",
        dataType: "text",
        data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            Success = true;//doesn't go here
        },
        error: function (textStatus, errorThrown) {
            Success = false;//doesn't go here
        }

    });
    //done after here
    return Success;
}

and Service:

[WebMethod]
public string SavePurpose(int Vid, int PurpId)
{
    try 
    {
        CHData.UpdatePurpose(Vid, PurpId);
        //List<IDName> abc = new List<IDName>();
        //abc.Add(new IDName { Name=1, value="Success" });
        return "Success";
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }
}

the service is being called Successfully from the AJAX. Value is also being Changed. But after the Service, success: or error: functions are not being called, in this case success should have been called but it is not working.

I used firebug and found that, the success or error functions are being skipped and goes directly to return Success;

Can’t seem to find what’s the problem with the code.

Update:
adding async: false fixed the problem

Answer 1

change your code to:

function ChangePurpose(Vid, PurId) {
    var Success = false;
    $.ajax({
        type: "POST",
        url: "CHService.asmx/SavePurpose",
        dataType: "text",
        async: false,
        data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            Success = true;
        },
        error: function (textStatus, errorThrown) {
            Success = false;
        }
    });
    //done after here
    return Success;
} 

You can only return the values from a synchronous function. Otherwise you will have to make a callback.

So I just added async:false, to your ajax call

Update:

jquery ajax calls are asynchronous by default. So success & error functions will be called when the ajax load is complete. But your return statement will be executed just after the ajax call is started.

A better approach will be:

     // callbackfn is the pointer to any function that needs to be called
     function ChangePurpose(Vid, PurId, callbackfn) {
        var Success = false;
        $.ajax({
            type: "POST",
            url: "CHService.asmx/SavePurpose",
            dataType: "text",
            data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
            contentType: "application/json; charset=utf-8",
            success: function (data) {
                callbackfn(data)
            },
            error: function (textStatus, errorThrown) {
                callbackfn("Error getting the data")
            }
        });
     } 

     function Callback(data)
     {
        alert(data);
     }

and call the ajax as:

 // Callback is the callback-function that needs to be called when asynchronous call is complete
 ChangePurpose(Vid, PurId, Callback);