public interface IFoo 

{

}

​

public class FakeNull : IFoo

{

    public override bool Equals(object obj)

    {

        if (obj == null)

        {

            return true;

        }

        return false;

    }

    public override int GetHashCode()

    {

        return 0;

    }

}

public class Program

{

    public static void Main()

    {

        FakeNull noInterface = new FakeNull();

        IFoo withInterface = new FakeNull();

        System.Console.WriteLine($"No Interface => {noInterface.Equals(null)}");

        System.Console.WriteLine($"Interface Broken => {withInterface == null}");

        System.Console.WriteLine($"Interface Fixed => {withInterface == null || withInterface.Equals(null)}");

    }

}