Spawn a new thread to open a new window and close it from a different thread

Question

Right now I have C# code to spawn a new window in a different thread, this works, but as soon as the new spawned window opens, it closes and the thread ends. How would I mak

Answer 1

You can do it like this:

In Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.Threading;

namespace TwoWindows
{
    static class Program
    {
        public static Form1 form1;
        public static Form2 form2;
        /// 

        /// The main entry point for the application.
        /// 
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false); 

            form1 = new Form1();
            form2 = new Form2();

            form1.Form2Property = form2;
            form2.Form1Property = form1;

            form1.Show();
            form2.Show();

            Application.Run();
        }
    }
}

In Form1.cs:

namespace TwoWindows
{
    public partial class Form1 : Form
    {
        public Form2 Form2Property { get; set; }

        public Form1()
        {
            InitializeComponent();
        }

        protected override void OnClosed(EventArgs e)
        {
            if (Form2Property.IsDisposed)
                Application.Exit();
        }
    }
}

And Form2.cs:

namespace TwoWindows
{
    public partial class Form2 : Form
    {
        public Form1 Form1Property { get; set; }

        public Form2()
        {
            InitializeComponent();
        }

        protected override void OnClosed(EventArgs e)
        {
            if (Form1Property.IsDisposed)
                Application.Exit();
        }
    }
}

This way you can get two forms on the same thread and use one to control the other one. If you need to use threads I would suggest to use dedicated threads that are part of the classes an not spawn in a method that can be called more than once. Then use ManualResetEvent or AutoResetEvent to control the thread processing. I really like the approach of using something like this, because is safe and doesn't spend much resources initialising threads.

public class MyClassOrForm
{
    Thread myProcessingThread;
    public AutoResetEvent startProcessing = new AutoResetEvent(false);
    public AutoResetEvent processingFinished = new AutoResetEvent(false);
    public AutoResetEvent killProcessingThread = new AutoResetEvent(false);

    public MyClassOrForm()
    {
        myProcessingThread = new Thread(MyProcess);
    }

    private void MyProcess()
    {
        while (true)
        {
            if (startProcessing.WaitOne())
            {
                // Do processing here

                processingFinished.Set();
            }

            if (killProcessingThread.WaitOne(0))
                return;
        }
    }
}

Then, once you have set the data to be processed, call form another class or method

MyClassOrMethodInstance.startProcessing.Set();

And if you need to wait for that processing to finish then insert:

MyClassOrMethodInstance.processingFinished.WaitOne(time_out_ms);

This is equivalent to a Thread.Join() call, only that you wont have to allocate another thread every time with the risks that threads entails if they depend on local data or unfinished child threads.