How often do you see code like this in your domain model?
public void Ship(int orderId, int customerId, string address) { Shipment shipment = _existingShipments.Single(x => x.OrderId == orderId); if (shipment.CustomerId == customerId) { // Do something  } }   Seems pretty good, doesn’t it? Well, it doesn’t. I’ve already pointed using Ids in domain entities as a bad practice, but I see developers - even sophisticated ones - write such code over and over again, so this topic definitely deserves a separate article.