Should IDisposable.Dispose() implementations be idempotent?

Question

The Microsoft.NET framework provides the IDisposable interface which requires an implementation of void Dispose() method. Its purpose is to enable

Answer 1

should the implementation of the Dispose() method be idempotent

Yes, it should. There is no telling how many times it will be called.

From Implementing a Dispose Method on MSDN:

a Dispose method should be callable multiple times without throwing an exception.

An object with a good implementation of IDispose will have a boolean field flag indicating if it has been disposed of already and on subsequent calls do nothing (as it was already disposed).