public static void Main() { AppDomain otherDomain = AppDomain.CreateDomain("otherDomain"); PingPong pp = new PingPong(); pp.MyCallBack(); pp.greetings = "PONG!"; otherDomain.DoCallBack(new CrossAppDomainDelegate(pp.MyCallBack)); // Output: // PING! from defaultDomain // PONG! from defaultDomain }