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 and SecondClass. FirstClass uses resources that must be disposed. SecondClass does not.

So the question is, where should I inherit from IDisposable? Both of the following options seem less than ideal:

1) Make FirstClass inherit IDisposable. Then, any code that deals with ISomeInterfaces will have to know whether or not to dispose of them. This smells like tight coupling to me.

2) Make ISomeInterface inherit IDisposable. Then, any class that inherits from it must implement IDisposable, even if there is nothing to dispose. The Dispose method would essentially be blank except for comments.

#2 seems like the correct choice to me, but I'm wondering if there are alternatives.

Answer 1

If there is a reasonable chance that an abstract entity (interface or abstract class) might need to be disposable, it should implement it. Stream, for example doesn't itself need IDisposable, nor does IEnumerator<T>...

An abstract base class may be simpler, as you can have a default (empty) implementation of Dispose() then, and possibly the finalizer / Dispose(bool) pattern, i.e.

~BaseType() => Dispose(false);

protected virtual void Dispose(bool disposing) 
{
}

void IDisposable.Dispose() 
{ 
    Dispose(true); GC.SuppressFinalize(this); 
}