Question

Hi i wanna still receiving 6 bytes from Serial Port only when is selected TabItem1.
And set checkboxes states depends on that bytes…
Example: but it not working :/

private void receiveData()
{            
    for(int i = 0; i < 3; ++i)          
        inputs[i] = serialPort.ReadByte();
    for (int i = 0; i < 3; ++i)          
        outputs[i] = serialPort.ReadByte();

    checkBoxI1.IsChecked = inputs[0] == 32 ? true : false;
    checkBoxI2.IsChecked = inputs[1] == 32 ? true : false;
    checkBoxI3.IsChecked = inputs[2] == 32 ? true : false;
    checkBoxQ1.IsChecked = outputs[0] == 32 ? true : false;
    checkBoxQ2.IsChecked = outputs[1] == 32 ? true : false;
    checkBoxQ3.IsChecked = outputs[2] == 32 ? true : false;
}
// Tab change
private void tabControl1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (tabControl1.SelectedItem == tabItem1)
    {                                     
        serialPort.Close();
        try
        {
            receiveThread.Abort();
        }
        catch (NullReferenceException)
        { 
        }
    }
    else if (tabControl1.SelectedItem == tabItem2)
    {                
        serialPort.Open();                
        receiveThread = new Thread(receiveData);
        receiveThread.Start();                
    }
}

Answer 1

I think the receiveData function is bound to the SerialPort.DataReceived event. This will in fact run on a different thread than your gui. And you like to change something on your gui which leads to the shown problem.

To let this work you should maybe call

checkBoxI1.Invoke(new Action(() => 
{
    checkBoxI1.IsChecked = inputs[0] == 32;
    checkBoxI2.IsChecked = inputs[1] == 32;
    checkBoxI3.IsChecked = inputs[2] == 32;
    checkBoxQ1.IsChecked = outputs[0] == 32;
    checkBoxQ2.IsChecked = outputs[1] == 32;
    checkBoxQ3.IsChecked = outputs[2] == 32;
}));

This will switch back to the gui thread to make these changes and the exception should be gone.