public ActionResult GetExpensesForCategory(string userName, string category)
 {
     if (ModelState.IsValid)
     {
         ExpenseItem[] results;
         if (string.IsNullOrEmpty(category))
         {
             results = ExpenseManager.GetExpenseItems(userName);
         }
         else
         {
             results = ExpenseManager.GetExpenseItemsByCategory(userName, category);
         }
         return(Json(results, JsonRequestBehavior.AllowGet));
     }
     else
     {
         return(new HttpStatusCodeResult(HttpStatusCode.NotFound));
     }
 }