“500: Unknown web method” when i send data using $.ajax and WebMethod-Collection of common programming errors

I’m trying to send data via Ajax to my database, using the JQuery Ajax function and and WebMethod in my C# code. But it’s not working. Any ideas?

$(function() {
    $('#Add').click(function() {
        var $dialog = $('

Originally posted 2013-11-09 19:43:34.