Displaying variable values not fast enough

Question

I have the following code which should send a series values through TCP/IP, each value modifies variables 'x', 'y' and 'z' in some way. When I get any response I want the code to display the current value of 'x', 'y' and 'z', but it doesn't. I've tried adding Sleep(), Timers, and even using Labels instead of textBoxes but nothing. Any ideas? Regards

for (i = 0; i < cant; i++)
        {
            byte[] data = null;
            aux = (Convert.ToInt32(v[i, 3] + 48, CultureInfo.InvariantCulture));

            //update variables' values
            x = x + Convert.ToInt32(v[i, 0]);
            y = y + Convert.ToInt32(v[i, 1]);
            z = z + Convert.ToInt32(v[i, 2]);

            data = System.BitConverter.GetBytes(aux);
            NetworkStream stream = client.GetStream();

            // String to store the response ASCII representation.
            String responseData = String.Empty;

            // Send the message to the connected TcpServer. 
            stream.Write(data, 0, 1);
            // Buffer to store the response bytes.
            data = new Byte[256];                
            while (responseData.Length == 0)
            {
                // Read the first batch of the TcpServer response bytes.
                Int32 bytes = stream.Read(data, 0, data.Length);
                responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes);
            }

            //DISPLAY CURRENT VALUES
            textBoxX.Text = x.ToString();
            textBoxY.Text = y.ToString();
            textBoxZ.Text = z.ToString();
        }

This is quite fundamental to the way Winforms or WPF works, the control doesn't get repainted until your code stops running and re-enters the message loop. Assuming Winforms, you could add textBoxX.Update() to force a paint. Not actually very practical, if you did it right then it would just look like a blur to human eyes. If it is important to see all values then use a ListBox instead. — Hans Passant, Mar 14 '12 at 16:24

score 2 · Accepted Answer · answered Mar 14 '12 at 16:28

I'm guessing that your text box / label / etc is not being given a chance to redraw as the above code is running in the main GUI thread of the application. The thread is busy doing that for loop so it can't process the repaint events. Sleep doesn't help as it puts the thread being put to sleep is the thread required to do the redraw.

To sort this out, you need to put the above loop into its own thread. This will allow the GUI thread a chance to redraw the controls. You need to use the Invoke method to update the controls as you'll get a cross thread execution error.

I did the above by creating a new thread delegate but it then had issues with cross-thread operations. You need to invoke call backs on variables as you change them. Source here: http://stackoverflow.com/questions/10775367/cross-thread-operation-not-valid-control-textbox1-accessed-from-a-thread-othe — bizah, Nov 05 '13 at 22:28

Displaying variable values not fast enough

1 Answers1