Declare IDisposable for the class or interface?

Question

Starting from the follwing situation:

public interface ISample
{
}

public class SampleA : ISample
{
   // has some (unmanaged) resources that needs to be di         


        

Answer 1

IDispoable being a very common interface, there's no harm having your interface inheriting from it. You will so avoid type checking in your code at the only cost to have a no-op implementation in some of your ISample implementations. So your 2nd choice might be better from this point of view.