Cannot cast between generic types

Question

I\'m trying to do this:

interface IA
{
}

class A : IA
{
}

class Foo where T: IA
{
}

class Program
{
    static void Main( string[] args )
    {
          


        

Answer 1

All generic classes are invariant. Interfaces (and delegates) on the other hand can support co- and contra-variance, but only in the cases where it's possible safely. And they need to opt-in explicitly.

For example via IFoo or IFoo