public void SubmitOrder(OrderData data) { // call the domain model for regular order submit logic var customer = GetCustomer(data.CustomerId); var shoppingCart = GetShoppingCart(data.CartId); // if (customer.UnpaidOrdersAmount + shoppingCart.Total > Max) // { // // fail (no discussion of exceptions vs returns codes here) // } // else // { // customer.Purchase(shoppingCart); // } customer.Purchase(shoppingCart); }