Question

in my app’ i’m recieving data from serial port and save them into two bool arrays.
And depends on these array i’m setting checkboxes. But checkboxes are not updating only when i change the tabs….

Here’s how i’m doin’ it(maybe there’s better way how to do it)

private void comboBoxCommunication_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (serialPort.IsOpen)
  {
    recieveThread.Abort();
        serialPort.Close();               
  }
  ComboBoxItem cbi = (ComboBoxItem)comboBoxCommunication.SelectedItem;
  portCommunication = cbi.Content.ToString();
  serialPort.PortName = portCommunication;
  try
  {
    serialPort.Open();
    recieveThread = new Thread(dataRecieving);
        prijmiThread.Start();                                
    checkBoxI1.IsChecked = vstupy[0] ? true : false;
    checkBoxI2.IsChecked = inputs[1] ? true : false;
    checkBoxI3.IsChecked = inputs[2] ? true : false;
    checkBoxQ2.IsChecked = outputs[3] ? true : false;                                           
  }
  catch (IOException ex)
  {
        MessageBox.Show(ex.ToString(), "Error!", MessageBoxButton.OK, MessageBoxImage.Error, MessageBoxResult.OK);
    }
}

private void dataRecieving()
{ 
    if (serialPort.IsOpen)
  {                    
    int i = serialPort.ReadChar();
    if (i == 'A')
    {
        inputs[0] = true;
    }
        else if (i == 'a')
        {
        inputs[0] = false;
    }
    if (i == 'B')
    {
        inputs[1] = true;
    }
    else if (i == 'b')
    {
        inputs[1] = false;
    }
    if (i == 'C')
    {
        inputs[2] = true;
    }
    else if (i == 'c')
    {
        inputs[2] = false;
    }
    if (i == 'D')
    {
        outputs[0] = true;
    }
    else if (i == 'd')
    {
        outputs[0] = false;
    }                        
  }           
}

Answer 1

Assuming you are tying to launch a thread that checks the serial port and then have your GUI update in near-real time to changes that come across the serial thread you probably need to do several things.

1. I would raise an event from the serial reading code when a checkbox changes state
2. The GUI could subscribe to this event BUT you have to be aware of cross threading. That is you can’t let the handler of the event directly update the GUI element owned by a separate thread.
3. So in your event handler you need to invoke the update via the owning thread.

I wrote up a blog entry once on an idiom for handling cross threading on Winform apps.

I’m also not sure how your inputs array is defined, but in general it’s not a good idea for two threads to be accessing shared data without some type of control mechanism. If your array is based on a data type that does atomic read/writes it might be OK but typically you want to consider what happens if one thread is in the middle of a non-atomic write when another thread either reads or writes the same data. Lots of material abounds on thread safety that you probably want to become familiar with.