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

Personally, if all ISample's should be disposable I'd put it on the interface, if only some are I'd only put it on the classes where it should be.

Sounds like you have the latter case.