Interface Covariance

InterfaceCovariance.cs

public interface ICovariantExample<out T>
{
    // Invalid variance
    // The type parameter 'T' must be contravariantly valid on 'ICovariantExample<T>.Go(T)'. 
    // 'T' is covariant.
    T Go();
}

public class CovariantExample<T> : ICovariantExample<T>
{
    public T Go() { Console.WriteLine("CovariantExample {0}", typeof(T).Name); return default(T); }
}


ICovariantExample<string> sout = new CovariantExample<string>();
sout.Go();
ICovariantExample<object> oout = sout;
oout.Go();