Interface with generic parameter vs Interface with generic methods

Question

Let\'s say I have such interface and concrete implementation

public interface IMyInterface
{
    T My();
}

public class MyConcrete : IMyInterface&l         


        

Answer 1

Because your interface declares a generic method T My(), but you implementation does not implement a function with that specific signature.

To achieve what you want, you need to provide the T generic parameter to the interface instead, in your first example:

public interface IMyInterface2
{
        T My();
}

public class MyConcrete2 : IMyInterface2
{
    public string My()
    {
        throw new NotImplementedException();
    }
}