public JsonResult UpdateCart(string productID, int quantity)
        {
            WCFCart_OrderClient coClient = new WCFCart_OrderClient();
            try
            {
                if (quantity > 0)
                {
                    //get cart product
                    Cart_Product cpToUpdate = coClient.GetCartProduct(@User.Identity.Name, new Guid(productID));

                    //change the quantity
                    cpToUpdate.Quantity = quantity;

                    //update
                    coClient.UpdateCart(cpToUpdate);

                    //refresh the list
                    List<Cart_Product> cp = coClient.GetCart(@User.Identity.Name).ToList();
                    //return PartialView("_Cart", cp);

                    return Json("success");
                }
                else
                {
                    return Json("error");
                }
            }
            catch (Exception e)
            {
                return Json("error");
            }
        }
        public ActionResult UpdateCart(string productID, int quantity)
        {
            WCFCart_OrderClient coClient = new WCFCart_OrderClient();

            //get cart product
            Cart_Product cpToUpdate = coClient.GetCartProduct(@User.Identity.Name, new Guid(productID));

            //change the quantity
            cpToUpdate.Quantity = quantity;

            //update
            coClient.UpdateCart(cpToUpdate);

            //refresh the list
            List<Cart_Product> cp = coClient.GetCart(@User.Identity.Name).ToList();
            //return PartialView("_Cart", cp);

            return Json(cp);
        }