Serialize(ModelState.Values.SelectMany(v > v. Errors)) , JsonRequestBehavior.AllowGet) This is a recent test (above) when I used an AJAX In jQuery, you can specify that you want either JSONP or JSON data returned from your AJAX calls.jubourg July 11, 2010. .jsonp provides complete, success and error callback . Removed proccessData: false because it doesnt affect jsonp requests and you arent passing any data. Added success: successFn so that jQuery will execute successFn on success with the parsed json data. Renamed callback to callbackName so that its more obvious about what it contains.