Наследование: Message
 public void Process(SayS2S msg, IOperationContext context)
 {
     foreach (var roomMember in _roomMembers)
     {
         roomMember.CallbackChannel.Send(new RoomEvent() { Text = msg.Text, UserName = msg.UserName });
     }
 }
 public Task Say(SayS2S msg)
 {
     _callbackChannel.OnRoomEvent(new RoomEvent() { Text = msg.Text, UserName = msg.UserName });
     return Task.FromResult(0);
 }