Why can a public class not inherit from a less visible one?
- by Dan Tao
I apologize if this question has been asked before. I've searched SO somewhat and wasn't able to find it.
I'm just curious what the rationale behind this design was/is. Obviously I understand that private/internal members of a base type cannot, nor should they, be exposed through a derived public type. But it seems to my naive thinking that the "hidden" parts could easily remain hidden while some base functionality is still shared and a new interface is exposed publicly.
I'm thinking of something along these lines:
Assembly X
internal class InternalClass
{
protected virtual void DoSomethingProtected()
{
// Let's say this method provides some useful functionality.
// Its visibility is quite limited (only to derived types in
// the same assembly), but at least it's there.
}
}
public class PublicClass : InternalClass
{
public void DoSomethingPublic()
{
// Now let's say this method is useful enough that this type
// should be public. What's keeping us from leveraging the
// base functionality laid out in InternalClass's implementation,
// without exposing anything that shouldn't be exposed?
}
}
Assembly Y
public class OtherPublicClass : PublicClass
{
// It seems (again, to my naive mind) that this could work. This class
// simply wouldn't be able to "see" any of the methods of InternalClass
// from AssemblyX directly. But it could still access the public and
// protected members of PublicClass that weren't inherited from
// InternalClass. Does this make sense? What am I missing?
}
