Getting derived object from the base object

Question

I extended the System.Net.Sockets.TcpClient class and I cannot figure out how to get an instance of my derived class when given an instance of the base TcpClient class. For example, the TcpListner.AcceptTcpClient() method returns a TcpClient object. I would like to take that and get an instance of my derived class. I tried to just cast it, but I get an invalid cast error - which I expected since the base object wasn't boxed from the derived object. I tried to just assign the base object in the constructor of the derived class: new MyTcpClient(TcpClient client) { base = client; } but it wouldn't compile - "Use of keyword base is not valid in this context". Can something like this even be done?

shimtanny · Answer

Hi Maybe it works to derive from Socket and then using TcpListener.AcceptSocket(). Then creating a TcpClient and assign the socket. ?? Simon

shimtanny · Answer

Hi I see the problem i mean i dont have a solution at the moment. A guy on the internet has the same problem: http://www.devhood.com/messages/message_view-2.aspx?thread_id=94141 Maybe it helps. Simon

jshepler · Answer

No I thought you understood the problem and was just verifying if you understood it correctly. Yes I have a class public class MyTcpClient : TcpClient { public int ResourceIndex = -1; private NetworkStream ns; public delegate void TcpObjectHandler (TCPClient client Infob iob); public event TcpObjectHandler ObjectArrived; public MyTcpClient() : base() {} public MyTcpClient(IPEndPoint localEP) : base(localEP) {} public MyTcpClient(AddressFamily family) : base(family) {} public MyTcpClient(string hostname int port) : base(hostname port) {} .... } Now I set up a TcpListener object that has a method AcceptTcpClient() which returns a TcpClient object. I need to take that object and get an instance of MyTcpClient. Doing this: TcpListener listener = new TcpListener(IPAddress.Any port); listener.Start(); while(true) { Thread.Sleep(1000); if(!listener.Pending()) continue; MyTcpClient newClient = (MyTcpClient)listener.AcceptTcpClient(); ... } fails during runtime - invalid cast exception. I expected this because the TcpClient object that AcceptTcpClient() returned wasn't boxed from MyTcpClient originally so the cast fails. My next attempt was to add another constructor to MyTcpClient that took an instance of TcpClient and tried to assign it to base like so: public MyTcpClient (TcpClient client) { base = client; } which failed to compile - cannot use the base keyword in that context. So my problem/question is - how do I get an instance of a derived object from an instance of the base object?

shimtanny · Answer

oubs sorry i thought the story has ended. Does the lines how to instantiate not help? I think i haven't got understood the problem. Sorry. Simon

jshepler · Answer

Sorry if I'm being pushy but any ideas yet?

jshepler · Answer

Yes that's it exactly.

shimtanny · Answer

Hi I am not sure what the situation is but maybe this helps: Is this your specialized tcp client? public class MyTcpClient : TcpClient { public MyTcpClient() : base() { } } To instantiate: MyTcpClient client = new MyTcpClient(); or... MyTcpClient client = (MyTcpClient) new TcpClient(); Have i understood the situation? Simon