Kooboo.Commerce.Carts.ShoppingCartService.AddItem C# (CSharp) Method

        public ShoppingCartItem AddItem(ShoppingCart cart, Product product, ProductVariant productPrice, int quantity)
        {
            Require.NotNull(cart, "cart");
            Require.NotNull(product, "product");
            Require.NotNull(productPrice, "productPrice");
            Require.That(quantity > 0, "quantity", "Quantity should be greater than zero.");

            var item = cart.Items.FirstOrDefault(i => i.ProductVariant.Id == productPrice.Id);
            if (item == null)
            {
                item = new ShoppingCartItem(productPrice, quantity, cart);
                AddItem(cart, item);
            }
            else
            {
                ChangeItemQuantity(cart, item, item.Quantity + quantity);
            }

            return item;
        }

        public int AddItem(int cartId, int productVariantId, int quantity)
        {
            var cartService = new Core.ShoppingCartService(_context.Instance);
            var cart = cartService.Find(cartId);
            var variant = new Kooboo.Commerce.Products.ProductService(_context.Instance).FindVariant(productVariantId);

            return _context.Database.Transactional(() =>
            {
                return cartService.AddItem(cart, variant.Product, variant, quantity).Id;
            });
        }