public ActionResult Add(OrderItemViewModel itemVM)
        {
            Session["itemVM"] = itemVM;
            Session["List"]   = TempData["List"];
            var order = service.temporaryList(itemVM, (List <OrderItemViewModel>)TempData["List"]);

            TempData["List"] = order.orderItem;
            TempData.Keep();
            return(Json(order, JsonRequestBehavior.AllowGet));
        }
        public OrderViewModel temporaryList(OrderItemViewModel itemVM, List <OrderItemViewModel> ListItem)
        {
            var result = service.temporaryList(itemVM, ListItem);

            return(result);
        }