make sure object only created by factory (C#)

Question

How do I make sure that a certain class is only instantiated by a factory and not by calling new directly?

EDIT: I need the factory

Answer 1

I do not like to have the factory on the type itself especially if it is a domain object. Have it internal if you are having a separate class as factory (which I think you should). Use InternalVisible attribute if the factory is on the different assembly.