public static void Case2() { { Cb bb = new Cb(); bb.WhoAmI(); (bb as Ca).WhoAmI(); } { Ca aa = new Ca(); aa.WhoAmI(); (aa as Cb)?.WhoAmI(); } }
static void WhoAmI(this Cb bb) { Console.WriteLine("static void WhoAmI(this Cb bb)"); bb.Func(); }