Asp.net C# Ajax call method WebForm

Question

I'm trying to create a username-check that sends a username to the server which will answer true or false. Every time sb left the textbox it sends the username. My idea was to create a ajax method that call a codebehind c# method. But it doesn't work.

Information: It is a WebForms Application

ASPX Code:

 <script type="text/javascript" src="/scripts/jquery-1.4.1.js"></script> <script type="text/javascript"> function checkUsername() { $.ajax({ type: 'POST', url: 'Default.aspx/checkUsername', data: JSON.stringify({ name: document.getElementById('txt_Username').value }), contentType: 'application/json; charset=utf-8', dataType: 'json', success: function (msg) { // (inform the user) alert(msg); }, error: function (err) { alert(err); } }); }); </script>

And the CodeBehind

[WebMethod]
public static string checkUsername(string name)
{
    //Get the server data
    return output;
}

I tried a lot of things with this code but nothing works!

Answer 1

change this

function checkUsername() {
   $.ajax({
         type: 'POST',
          url: 'Default.aspx/checkUsername',
          data: JSON.stringify({ name: document.getElementById('txt_Username').value }),
          contentType: 'application/json; charset=utf-8',
          dataType: 'json',
          success: function (msg) {
              // (inform the user)
              alert(msg);
           },
           error: function (err) {
                    alert(err);
            }
            });
        });

to

    function checkUsername() {
      var obj = { "name": $('txt_Username').val() }
       $.ajax({
              type: "POST",
              contentType: "application/json; charset=utf-8",
              url: "Default.aspx/checkUsername",
              data: JSON.stringify(obj),
              dataType: "json",
              success: function (msg) {
                  // (inform the user)
                  alert(msg);
               },
               error: function (err) {
                        alert(err);
                }
                });
            });