public static void VirtualFunc(out int r1, out int r2)
        {
            BaseClass o1 = new BaseClass();
            BaseClass o2 = new DrivenClass();

            r1 = o1.Foo();
            r2 = o2.Foo();
        }
        public static int ItfWithRefParam(ref int a, out int b)
        {
            ItfWithRefParam o = new DrivenClass();

            return(o.WithRefParam(ref a, out b));
        }