How to display error message using MVC error handler(Customized) and jqgrid Load error trigger

public ActionResult Addtemp(typebaker postData)
       {
           string status = "";
              Classtypebaker _Classbaker = new Classtypebaker();
              //todo: Add temp to repository
              if (postData == null)
                  return Json(false);
              int baker = _Classbaker.checkbaker(postData.FNameTypeBaker);
              if (baker <= 0)
            {
                db.typebakers.Add(postData);
                db.SaveChanges();
                return Json(true);
            }
              else
              {

                  status = "this test";

                  return Json(new     {status},JsonRequestBehavior.AllowGet);

              }
            ///  return Json(true);
          }