public ActionResult CartSummary()
        {
            var cart = new ShoppingCartService(HttpContext);

            ViewData["CartCount"] = cart.Count();

            return PartialView("CartSummary");
        }
        public ActionResult AddToCart(int id)
        {
            var cart = new ShoppingCartService(HttpContext);

            cart.Add(id);

            return RedirectToAction("index");
        }
        // GET: ShoppingCart
        public ActionResult Index()
        {
            var cart = new ShoppingCartService(HttpContext);
            var items = cart.GetCartItems();

            return View(new ShoppingCartViewModel
            {
                Items = items,
                Total = CalcuateCart(items)
            });
        }
        public ActionResult Checkout(CheckoutViewModel model)
        {
            if (!ModelState.IsValid)
            {
                return View(model);
            }

            var cart = new ShoppingCartService(HttpContext);

            var result = cart.Checkout(model);

            if (result.Message=="Pass")
            {
                TempData["transactionId"] = result.TransactionId;
                cart.ClearCart(HttpContext);
                return RedirectToAction("Complete");
            }

            ModelState.AddModelError(string.Empty, result.Message);

            return View(model);
        }
        public ActionResult RemoveFromCart(int id)
        {
            var cart = new ShoppingCartService(HttpContext);

            cart.Remove(id);

            return RedirectToAction("index");
        }