Ajax success event not working

The result is probably not in JSON format, so when jQuery tries to parse it as such, it fails. You can catch the error with error: callback function.

You don't seem to need JSON in that function anyways, so you can also take out the dataType: 'json' row.

Although the problem is already solved i add this in the hope it will help others.

I made the mistake an tried to use a function directly like this (success: OnSuccess(productID)). But you have to pass an anonymous function first:

  function callWebService(cartObject) {

    $.ajax({
      type: "POST",
      url: "http://localhost/AspNetWebService.asmx/YourMethodName",
      data: cartObject,
      contentType: "application/x-www-form-urlencoded",
      dataType: "html",
      success: function () {
        OnSuccess(cartObject.productID)
      },
      error: function () {
        OnError(cartObject.productID)
      },
      complete: function () {
        // Handle the complete event
        alert("ajax completed " + cartObject.productID);
      }
    });  // end Ajax        
    return false;
  }

If you do not use an anonymous function as a wrapper OnSuccess is called even if the webservice returns an exception.