title: detect ajax request by jquery
body: <p>I'm working with asp controls and I have some dropdownlist which in selection go back to the server and do some action ( via asp ajax )
  what I'm l looking for is detecting via jquery when the ajax call is starting 
  I've tried the following call :</p>
  
  <pre><code>  $.ajaxSetup({
                      beforeSend: function (jqXHR, settings) {
                          alert("ok");
                          return false;
                      }
                  });
  </code></pre>
  
  <p>and </p>
  
  <pre><code>also  $(document).ajaxStart(function () {
                     alert("OK");
                  });
  </code></pre>
  
  <p>but none of this worked</p>