Question

I am new to C# and I am having a problem. I have a Form that runs a thread which receives input from a serial port. However when the window is closed the thread keeps running. I tried overriding virtual void OnClosing(object sender, CancelEventArgs e) but the MessageBox keeps popping up which means the thread is still running. What am I doing wrong? Which is the best lifecycle method to override to do cleanup before the window is closed?

DisplayForm.cs

using System;
using System.ComponentModel;
using System.Drawing;
using System.IO.Ports;
using System.Threading;
using System.Windows.Forms;

namespace project
{
    public partial class DisplayForm : Form
    {
        private Thread readThread;
        private SerialPort port;
        private bool running;

        public DisplayForm(String portName)
        {
            InitializeComponent();


            port = new SerialPort(portName);
            port.Open();

            readThread = new Thread(Read);
            running = true;
            readThread.Start();
        }

        public void Read()
        {
            while (running)
            {
                try
                {
                    string message = port.ReadLine();
                    Console.Write(message);
                    MessageBox.Show(message);
                }
                catch (TimeoutException)
                {

                }
            }
        }

        protected virtual void OnClosing(object sender, CancelEventArgs e)
        {
            running = false;
            readThread.Join();
            port.Close();
        }
    }
}

Answer 1

You need to use Abort() and not Join().

protected virtual void OnClosing(object sender, CancelEventArgs e) 
{ 
    running = false; 
    readThread.Abort();
    port.Close(); 
}