Generic Class Covariance

Question

Is it possible to make the following code compile in C#? I do compile similar in Java.

public interface IInterface
{
    ...
}

public class Class1 : IInterf         


        

Answer 1

No, that is not legal in C#. C# 4 and above support covariance and contravariance of generic interfaces and generic delegates when they are constructed with reference types. So for example, IEnumerable is covariant, so you could say:

List giraffes = new List() { ... };
IEnumerable animals = giraffes;

but not

List animals = giraffes;

Because a list of animals can have a tiger inserted into it, but a list of giraffes cannot.

Do a web search on covariance and contravariance in C# and you'll find lots of articles on it.