IList using covariance and contravariance in c#, is this possible?

Question

would this be possible? (I don't have vs. 2010, so I can't try it myself, sorry)

public interface IComplexList<out TOutput, in TInput> where TOutput : TInput
{
    public IEnumerator<TOutput> GetEnumerator();
    public void Add(TInput item);
}

public interface IList<T> : IComplexList<T, T>
{
}

If I get it right, you could use this to actually implement covariance and contravariance in the same interface.

Answer 1

No, you can't. In your example IList<T> is invariant. IList<T> would require to declare in/out to be covariant/contravariant. It's not possible to do that just by inheriting some interface that is covariant.