public RedirectToRouteResult AddItemToCart(CartFunctions cartFunctions, int productId, string url)
        {
            Product product = db.Products.FirstOrDefault(m => m.ProductId == productId);

            if (product != null)
            {
                cartFunctions.AddItem(product, 1);
            }
            return(RedirectToAction("CartSummary", new { url }));
        }