How should I inherit IDisposable?

Question

Class names have been changed to protect the innocent.

If I have an interface named ISomeInterface. I also have classes that inherit the interface, FirstClass

Answer 1

All of the answers written so far miss a key point: it's only necessary for a base type or base interface to implement IDisposable if it's likely that code which expects an base-class instance might otherwise acquire ownership of an instance which requires disposal without realizing it. The most common scenario via which this may occur is with a factory method; a prime example is IEnumerable/IEnumerator. Most enumerators do not require cleanup, but code which calls IEnumerable.GetEnumerator generally has no particular reason to believe that the returned enumerator will actually require cleanup, nor to believe that it won't. It's generally faster to have all implementations of IEnumerator implement IDisposable, and have all consumers call Dispose on the returned enumerator, than to have consumers check whether the returned type implements IDisposable and call it if so.

If it is expected that base-type references will generally only be used by methods which will not be responsible for cleaning up the items in question, there is no need for the base type to implement IDisposable. The code which would be responsible for cleanup will know that the objects it's dealing with implement IDisposable whether or not the base type does.