public ActionResult AddToShoppingCartCommand(int productId, int quantity = 1) { var cart = RetrieveCurrentShoppingCart(); cart = _service.AddProductToShoppingCart(cart, productId, quantity); SaveCurrentShoppingCart(cart); // PRG (Post-Redirect-Get) pattern to avoid F5 refresh issues // (and also key step to neatly separate Commands from Queries in the future) return(RedirectToAction("AddTo")); }