aspx and jquery.ajax is always returning an error

Question

This code worked fine in mvc2, but moving back to traditional ASPX (because of Sharepoint 2010). I am encountering errors. Can anyone tell me what I am doing wrong for this framework?

This ajax call is in the $.ready

$.ajax({
        type: "POST",
        dataType: "json",
        data: 'siteName=a&siteUrl=b',
        url: 'Wizard.aspx/DoesNameUrlExist',
        beforeSend: function () { alert("before send"); },
        complete: function () { alert("complete"); },
        success: function (data) { alert("success"); },
        error: function (data) {
            if ($("meta[name=debug]").attr("content") == "true") {
                //Full Error when debugging
                var errDoc = window.open();
                errDoc.document.write(data.responseText);
                errDoc.document.close();
            }
            else {
                // generic error message for production use
                alert("An unexpected error occurred.");
            } return false;
        }
    });

code behind

[WebMethod]
public static string DoesNameUrlExist(string siteName, string siteUrl)
{
    //do something
    return someString;
}

I get an error everytime.

Answer 1

You need to send JSON to the service and indicate that you're doing so via the contentType header:

$.ajax({
    type: "POST",
    contentType: 'application/json',
    data: '{"siteName":"a","siteUrl":"b"}',
    url: 'Wizard.aspx/DoesNameUrlExist',
    beforeSend: function () { alert("before send"); },
    complete: function () { alert("complete"); },
    success: function (data) { alert("success"); },
    error: function (data) {
        if ($("meta[name=debug]").attr("content") == "true") {
            //Full Error when debugging
            var errDoc = window.open();
            errDoc.document.write(data.responseText);
            errDoc.document.close();
        }
        else {
            // generic error message for production use
            alert("An unexpected error occurred.");
        } return false;
    }
});

More info here: http://encosia.com/using-jquery-to-directly-call-aspnet-ajax-page-methods/

Also, if you're using jQuery 1.4, you can drop the dataType. jQuery will infer JSON automatically based on the response's Content-Type header.