问WPF TextBlock更新

EN

 public Lobby()
    {
        InitializeComponent();
        ctThread = new Thread(getMessage);
        ctThread.Start();
        clientSocket.Connect("127.0.0.1", 8888);
        serverStream = clientSocket.GetStream();
    }

    TcpClient clientSocket = new System.Net.Sockets.TcpClient();
    NetworkStream serverStream = default(NetworkStream);
    string readData = null;
    Thread ctThread;


    private void btnSend_Click(object sender, RoutedEventArgs e)
    {
        byte[] outStream = System.Text.Encoding.ASCII.GetBytes(txtInput.Text);
        serverStream.Write(outStream, 0, outStream.Length);
        serverStream.Flush();
    }

    private void getMessage()
    {
        while (true)
        {
            serverStream = clientSocket.GetStream();
            int buffSize = 0;
            byte[] inStream = new byte[10025];
            buffSize = clientSocket.ReceiveBufferSize;
            serverStream.Read(inStream, 0, buffSize);
            string returndata = System.Text.Encoding.ASCII.GetString(inStream);
            readData = "" + returndata;
            Dispatcher.BeginInvoke(new Action(() =>
                {
                        txtContent.Text = txtContent.Text + Environment.NewLine + " >> " + readData;
                }));
        }
    }