public inheritance and tlb files

Question

Say you have two assemblies (two dlls). The first contains a class called Base and the second contains a class called Derived which publicly inherits from Base.

When I use the tlb files to create C++ classes in Visual Studio 2005, I get Base and Derived classes, but one is not a subclass of the other. There doesn't seem to be any IS-A relationship. Is there a reason for this?

Answer 1

I'm assuming here, that the two assemblies communicate one with the other via COM, if that is indeed the case then you are correct, there is no IS-A relationship in COM in regard to CLASS inheritance, only in regard to Interface inheritance.

If you were to define an interface IBase and IDerived which derives from IBase, then you would be able to cast IDerived to IBase on the same object which implements both.