Label won't change color until after code is finished executing

Question

It's a lot of irrelevant code to look through.. but pretty much it sends a packet and listens for a packet in return

if i comment the part out where it calls the ReceiveAuthPacket() method at the end of sending a packet, it will work and the label will turn blue.. but otherwise it will never activate turning the label blue and will instead turn the label red or green (depending on the returned packet).

basically im just using the label as an indicator of the status.. and no matter what i try i can't get it to turn blue because it seems to be waiting for all the code to be finished executing and it just won't work..

i even tried using data triggers in WPF and it still won't work.

any work arounds? i just don't get it..

        private readonly UdpMessageAuthentication _msgAuth;        

        private void Button_Authenticate_OnClick(object sender, RoutedEventArgs e)
        {
            Label_Authentication.Content = "Attempting Authentication";
            Label_Authentication.Foreground = new SolidColorBrush(Colors.Blue);

            _msgAuth.SendAuthPacket(IPAddress.Parse(TextBox_IP.Text), TextBox_ClientID.Text);
        }

        public void SendAuthPacket(IPAddress ip, string userID)
        {
            _ip = ip;
            _userID = userID;
            if (_udpClient.Client == null)
                _udpClient = new UdpClient();

            //GSISClockRegRequest,<Client Id>,,1 
            string msg = string.Format("GSISClockRegRequest,{0},,1", _userID);
            byte[] sendBytes = Encoding.ASCII.GetBytes(msg);
            bool sent = false;

            try
            {
                _label.Content = "Attempting Authentication";
                _label.Foreground = new SolidColorBrush(Colors.Blue);

                while (_label.Content != "Attempting Authentication")
                {
                    //loop
                }

                _udpClient.Connect(_ip, 5001);
                _udpClient.Send(sendBytes, sendBytes.Length);
                Console.WriteLine("Sending {0} bytes.  Message: {1}", sendBytes.Length, msg);
                sent = true;
            }
            catch (Exception)
            {
                Console.WriteLine("UDP Auth Packet Failed to Send");
            }

            _udpClient.Close();

            if (sent)
                ReceiveAuthPacket();  //IF I COMMENT THIS OUT IT'LL WORK
        }

        private void ReceiveAuthPacket()
        {
            IPEndPoint e = new IPEndPoint(IPAddress.Any, 5001);
            UdpClient u = new UdpClient(e);
            u.Client.ReceiveTimeout = 3000;
            Console.WriteLine("Listening for Messages: ");

            try
            {
                Byte[] receiveBytes = u.Receive(ref e);
                string receiveString = Encoding.ASCII.GetString(receiveBytes);
                Console.WriteLine("Received: {0}", receiveString);

                string errMsg = "";
                if (AuthMessageParser.ParseMessage(receiveString, ref errMsg))
                {
                    _label.Content = "Authentication Successful!";
                    _label.Foreground = new SolidColorBrush(Colors.Green);
                }
                else
                {
                    _label.Content = "Authentication Unsuccessful: " + errMsg;
                    _label.Foreground = new SolidColorBrush(Colors.Red);
                }

            }
            catch (Exception)
            {
                _label.Content = "Authentication Unsuccessful";
                _label.Foreground = new SolidColorBrush(Colors.Red);
                Console.WriteLine("UDP Auth Packet was NOT Received.");
            }

            u.Close();
        }

Answer 1

Your UI thread is blocked by calls to things like _udpClient.Connect() and _udpClient.Send() (and the receives, too)

A workaround would be to leverage the task parallel library and perform communications asynchronously to avoid blocking the UI thread.

It will manage threads for you as long as you define tasks properly. Holler if you need an example.

protected void SomeButton_Click(Object sender, EventArgs e)
{
    // Task off the work and do not wait, no blocking here.
    Task.Run(PerformConnection);
}

private async Task PerformConnection()
{
    // This method acts the way a thread should.  We await the result of async comms.
    // This will not block the UI but also may or may not run on its own thread.
    // You don't need to care about the threading much.
    var conn = await ListenerOrSomething.AwaitConnectionsAsync( /* ... */ );

    // Now you have your result because it awaited.
    using(var newClient = conn.Client())
    {
        var buffer = new byte[];           
        var recv = await newClient.ReceiveAsyncOrSomething(out buffer);

        // Data received is not zero, process it or return
        if(recv > 0)
            newClient.Response = await ProcessRequest(buffer);
        else
            return;
    }
}