Question

This is my 1st C# project so I may be doing something obviously improper in the code below.
I am using .NET, WinForms (I think), and this is a desktop application until I get the bugs out.
UpdateGui() uses Invoke((MethodInvoker)delegate to update various GUI controls based on received serial data and
sends a GetStatus() command out the serial port 4 times a second.
Thread Read() reads the response from serial port whenever it arrives which should be near immediate.
SerialPortFixer is a SerialPort IOException Workaround in C# I found at
http://zachsaw.blogspot.com/2010/07/serialport-ioexception-workaround-in-c.html.

After one or both threads die I’ll see something like
The thread 0x1288 has exited with code 0 (0x0).
in the debug code output.

Why do UpdateGui() and/or Read() eventually die?

public partial class UpdateStatus : Form
{
    private readonly byte[] Command = new byte[32];
    private readonly byte[] Status = new byte[32];
    readonly Thread readThread;
    private static readonly Mutex commandMutex = new Mutex();
    private static readonly Mutex statusMutex = new Mutex();
    ...

    public UpdateStatus()
    {
        InitializeComponent();
        SerialPortFixer.Execute("COM2");
        if (serialPort1.IsOpen)
        {
            serialPort1.Close();
        }
        try
        {
            serialPort1.Open();
        }
        catch (Exception e)
        {
            labelWarning.Text = LOST_COMMUNICATIONS + e;
            labelStatus.Text = LOST_COMMUNICATIONS + e;
            labelWarning.Visible = true;
        }
        readThread = new Thread(Read);
        readThread.Start();
        new Timer(UpdateGui, null, 0, 250);
    }
    static void ProcessStatus(byte[] status)
    {
        Status.State = (State) status[4];
        Status.Speed = status[6]; // MSB
        Status.Speed *= 256;
        Status.Speed += status[5];
        var Speed = Status.Speed/GEAR_RATIO;
        Status.Speed = (int) Speed;
        ...
    }
    public void Read()
    {
        while (serialPort1 != null)
        {
            try
            {
                serialPort1.Read(Status, 0, 1);
                if (Status[0] != StartCharacter[0]) continue;
                serialPort1.Read(Status, 1, 1);
                if (Status[1] != StartCharacter[1]) continue;
                serialPort1.Read(Status, 2, 1);
                if (Status[2] != (int)Command.GetStatus) continue;
                serialPort1.Read(Status, 3, 1);
                ...
                statusMutex.WaitOne();
                ProcessStatus(Status);
                Status.update = true;
                statusMutex.ReleaseMutex();
            }
            catch (Exception e)
            {
                Console.WriteLine(@"ERROR! Read() " + e);
            }
        }
    }
    public void GetStatus()
    {
        const int parameterLength = 0; // For GetStatus
        statusMutex.WaitOne();
        Status.update = false;
        statusMutex.ReleaseMutex();
        commandMutex.WaitOne();
        if (!SendCommand(Command.GetStatus, parameterLength))
        {
            Console.WriteLine(@"ERROR! SendCommand(GetStatus)");
        }
        commandMutex.ReleaseMutex();
    }
    private void UpdateGui(object x)
    {
        try
        {                
            Invoke((MethodInvoker)delegate
            {
                Text = DateTime.Now.ToLongTimeString();
                statusMutex.WaitOne();
                if (Status.update)
                {
                    if (Status.Speed > progressBarSpeed.Maximum)
                    {
                        Status.Speed = progressBarSpeed.Maximum;
                    }
                    progressBarSpeed.Value = Status.Speed;
                    labelSpeed.Text = Status.Speed + RPM;
                    ...
                }
                else
                {
                    labelWarning.Text = LOST_COMMUNICATIONS;
                    labelStatus.Text = LOST_COMMUNICATIONS;
                    labelWarning.Visible = true;
                }
                statusMutex.ReleaseMutex();
                GetStatus();
            });
        }
        catch (Exception e)
        {
            Console.WriteLine(@"ERROR! UpdateGui() " + e);
        }
    }
}

Answer 1

A thread will terminate when there’s no more code to execute, or more specifically when the method you specify when you create thread returns.

Maybe serialport1 becomes null?

As for the update timer, there is a special purpose windows forms timer that runs periodically that doesn’t require you to use Invoke. It’s the right tool for the job