C# handler not creating and failing when using .CreateHandler()

Question

I'm creating a game in which I use TCP/IP connection. The problem is that I'm using .Invoke to help me receive and send message.

The program goes like this: I'm my first window, i'm starting and connecting to the server like this :

{
        TcpListener listener = new TcpListener(IPAddress.Any, this.port);
        listener.Start();
        try {
            this.client = listener.AcceptTcpClient();
            gameWindow = new GameWindow(this.client, true);
            gameWindow.StartGame();
        }
}

then i'm connecting to it like this:

{
IPEndPoint ipEnd = new IPEndPoint(this.serverIP, this.port);
        {
            try {
                client.Connect(ipEnd);
                if (client.Connected) { 
                    gameWindow = new GameWindow(this.client, false);
                    gameWindow.StartGame();
                }
            }
}

The constructor for gameWindow (which is a form) looks like this:

public GameWindow(TcpClient thisClient, bool isServer)
    {
        InitializeComponent();
        this.client = thisClient;
        this.reader = new StreamReader(thisClient.GetStream());
        this.writer = new StreamWriter(thisClient.GetStream());

        this.writer.AutoFlush = true;

    }

I must wait for the server to send a message to the client, and then start the client ( I have a function .startGame() that uses .ShowDialog() and creates some pictureBoxs)

But nowhere I can get my handle created. I've tried to put this.createHandle() (read about it here) into GameWindow_Load but still not works. If I try to send a message with: workerSendData.RunWorkerAsync(); I get:

Additional information: Invoke or BeginInvoke cannot be called on a control until the window handle has been created.

What can I do to get my handler created? Using Thread.Sleep will sleep my whole UI, which does not work (a "solution" found on the internet)

My code for sending message :

 private void workerSendData_DoWork(object sender, DoWorkEventArgs e)
    {
        if (client.Connected) {
            this.writer.WriteLine(this.toSend); // aici trimitem datele.
            // de modificat : aici vom adauga in lista noastra miscarile.
            this.Invoke(new MethodInvoker(delegate () { MessageBox.Show("Me:" + this.toSend + "\n"); }));
        }
        else {
            MessageBox.Show("Send failed");
        }
        workerSendData.CancelAsync();
    }

My code for receiving data:

  private void workerReceiveData_DoWork(object sender, DoWorkEventArgs e)
    {
        while (client.Connected) {
            try {
                this.received = this.reader.ReadLine();
                this.myTurn = true;
                this.Invoke(new MethodInvoker(delegate () {
                    MessageBox.Show("This has been received: " + this.received);
                    /*this.tbReceive.AppendText("You:" + this.received + "\n");*/
                }));
                this.received = "";
            }
            catch (Exception x) {
                MessageBox.Show(x.Message.ToString());
            }
        }
    }

Inside the`Load` event the handle is already created. Use the `CreateHandle` method after you instantiate your class from outside. — abto, Jan 15 '17 at 08:53

score 0 · Answer 1 · edited May 23 '17 at 12:08

It seems that you cannot invoke an action before the Window is fully initialized and loaded. Assuming you are working in Windows Forms, there is a solution provided by @Greg D on this question, but it doesn't be to be the safest way to go.

I would suggest that you try to find a way to start the worker only after the window is loaded (for example using the Loaded event), so that the handle is definitely ready and this situation does not occur.

C# handler not creating and failing when using .CreateHandler()

1 Answers1