C# Receiving remote commands over TCP and invoking them on WinForm (Multithreaded)

Question

I have a console that I want to use to invoke commands on a WinForm in another computer (I'm testing it through localhost though).

When the form starts, it instantiates the CommandListener to receive commands over TCP. Whenever I attempt to instantiate it without a separate thread, the winform doesn't display at all, so I used "Initialize" to run it on a separate thread.

    public CommandListener(Form client)
    {
        this.ClientControl = client;

        Socket CommandSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        IPAddress ipa = IPAddress.Loopback;
        IPEndPoint ipe = new IPEndPoint(ipa, 23120);

        CommandSocket.Bind(ipe);
        CommandSocket.Listen(1);

        Thread RemoteCommandListener = new Thread(new ParameterizedThreadStart(Initialize));
        RemoteCommandListener.Start(CommandSocket);

    }

    private void Initialize(object obj)
    {
        Socket CommandSocket = (Socket)obj;

        while (true)
        {
            allDone.Reset();
            CommandSocket.BeginAccept(new AsyncCallback(AcceptCallback), CommandSocket);
            allDone.WaitOne();
        }
    }

Unfortunately, if I do use a separate thread, I receive "cross thread operation not valid" as an error when attempting to invoke the command on the winform.

            int bytesRead = Master.EndReceive(ar);
            if (bytesRead > 0)
            {
                state.sb.Append(Encoding.ASCII.GetString(state.Buffer, 0, bytesRead));

                command = state.sb.ToString();
                if (command.IndexOf("Write") > -1)
                {
                    try
                    {
                        MethodInfo method = typeof(Multiboxxy).GetMethod(command);
                        method.Invoke(ClientControl, new object[] { "Success!" });
                    }
                    catch (Exception e)
                    {
                        MessageBox.Show(e.InnerException.Message);
                    }
                }
                else
                {
                    Master.BeginReceive(state.Buffer, 0, StateObject.BufferSize, 0,
                       new AsyncCallback(ReadCallback), state);
                }
            }

Answer 1

I recommend using WCF instead; there is an option in WCF to synchronize automatically to the SynchronizationContext of the host.

The next-best option is to use automatically-synchronizing socket objects such as those in Nito.Async.

A third option is to keep the .NET Socket class but when you need to do UI updates, use a Task scheduled to the UI thread (TaskScheduler.FromCurrentSynchronizationContext). Task and TaskScheduler are built into .NET 4.0 and are available in a library for .NET 3.5.

A fourth option is to keep the .NET Socket class and use SynchronizationContext directly for updating the UI.

Answer 2

Instead of MethodInfo.Invoke, use:

// somewhere, define a delegate type for the invoked method (e.g. 'InvokerDelegate')

if (ClientControl.InvokeRequired)
    ClientControl.Invoke(Delegate.CreateDelegate(typeof(InvokerDelegate), ClientControl, method), "Success!");
else
    method.Invoke(ClientControl, new object[] { "Success!" });

The Control class' Invoke() method is, to the best of my knowledge, the only way to perform proper thread synchronization when calling methods on controls.