Capture console exit C#

Question

I have a console application that contains quite a lot of threads. There are threads that monitor certain conditions and terminate the program if they are true. This termination can happen at any time.

I need an event that can be triggered when the program is closing so that I can cleanup all of the other threads and close all file handles and connections properly. I'm not sure if there is one already built into the .NET framework, so I'm asking before I write my own.

I was wondering if there was an event along the lines of:

MyConsoleProgram.OnExit += CleanupBeforeExit;

Answer 1

I am not sure where I found the code on the web, but I found it now in one of my old projects. This will allow you to do cleanup code in your console, e.g. when it is abruptly closed or due to a shutdown...

[DllImport("Kernel32")]
private static extern bool SetConsoleCtrlHandler(EventHandler handler, bool add);

private delegate bool EventHandler(CtrlType sig);
static EventHandler _handler;

enum CtrlType
{
  CTRL_C_EVENT = 0,
  CTRL_BREAK_EVENT = 1,
  CTRL_CLOSE_EVENT = 2,
  CTRL_LOGOFF_EVENT = 5,
  CTRL_SHUTDOWN_EVENT = 6
}

private static bool Handler(CtrlType sig)
{
  switch (sig)
  {
      case CtrlType.CTRL_C_EVENT:
      case CtrlType.CTRL_LOGOFF_EVENT:
      case CtrlType.CTRL_SHUTDOWN_EVENT:
      case CtrlType.CTRL_CLOSE_EVENT:
      default:
          return false;
  }
}


static void Main(string[] args)
{
  // Some biolerplate to react to close window event
  _handler += new EventHandler(Handler);
  SetConsoleCtrlHandler(_handler, true);
  ...
}

Update

For those not checking the comments it seems that this particular solution does not work well (or at all) on Windows 7. The following thread talks about this

Answer 2

Full working example, works with ctrl-c, closing the windows with X and kill:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

namespace TestTrapCtrlC {
    public class Program {
        static bool exitSystem = false;

        #region Trap application termination
        [DllImport("Kernel32")]
        private static extern bool SetConsoleCtrlHandler(EventHandler handler, bool add);

        private delegate bool EventHandler(CtrlType sig);
        static EventHandler _handler;

        enum CtrlType {
            CTRL_C_EVENT = 0,
            CTRL_BREAK_EVENT = 1,
            CTRL_CLOSE_EVENT = 2,
            CTRL_LOGOFF_EVENT = 5,
            CTRL_SHUTDOWN_EVENT = 6
        }

        private static bool Handler(CtrlType sig) {
            Console.WriteLine("Exiting system due to external CTRL-C, or process kill, or shutdown");

            //do your cleanup here
            Thread.Sleep(5000); //simulate some cleanup delay

            Console.WriteLine("Cleanup complete");

            //allow main to run off
            exitSystem = true;

            //shutdown right away so there are no lingering threads
            Environment.Exit(-1);

            return true;
        }
        #endregion

        static void Main(string[] args) {
            // Some boilerplate to react to close window event, CTRL-C, kill, etc
            _handler += new EventHandler(Handler);
            SetConsoleCtrlHandler(_handler, true);

            //start your multi threaded program here
            Program p = new Program();
            p.Start();

            //hold the console so it doesn’t run off the end
            while (!exitSystem) {
                Thread.Sleep(500);
            }
        }

        public void Start() {
            // start a thread and start doing some processing
            Console.WriteLine("Thread started, processing..");
        }
    }
}

Answer 3

Check also:

AppDomain.CurrentDomain.ProcessExit

Answer 4

It sounds like you have the threads directly terminating the application? Perhaps it would be better to have a thread signal the main thread to say that the application should be terminated.

On receiving this signal, the main thread can cleanly shutdown the other threads and finally close itself down.

Answer 5

There is for WinForms apps;

Application.ApplicationExit += CleanupBeforeExit;

For Console apps, try

AppDomain.CurrentDomain.DomainUnload += CleanupBeforeExit;

But I am not sure at what point that gets called or if it will work from within the current domain. I suspect not.

Answer 6

I've had a similar problem, just my console App would be running in infinite loop with one preemptive statement on middle. Here is my solution:

class Program
{
    static int Main(string[] args)
    {
        // Init Code...
        Console.CancelKeyPress += Console_CancelKeyPress;  // Register the function to cancel event

        // I do my stuffs

        while ( true )
        {
            // Code ....
            SomePreemptiveCall();  // The loop stucks here wating function to return
            // Code ...
        }
        return 0;  // Never comes here, but...
    }

    static void Console_CancelKeyPress(object sender, ConsoleCancelEventArgs e)
    {
        Console.WriteLine("Exiting");
        // Termitate what I have to terminate
        Environment.Exit(-1);
    }
}

Answer 7

ZeroKelvin's answer works in Windows 10 x64, .NET 4.6 console app. For those who do not need to deal with the CtrlType enum, here is a really simple way to hook into the framework's shutdown:

class Program
{
    private delegate bool ConsoleCtrlHandlerDelegate(int sig);

    [DllImport("Kernel32")]
    private static extern bool SetConsoleCtrlHandler(ConsoleCtrlHandlerDelegate handler, bool add);

    static ConsoleCtrlHandlerDelegate _consoleCtrlHandler;

    static void Main(string[] args)
    {
        _consoleCtrlHandler += s =>
        {
            //DoCustomShutdownStuff();
            return false;   
        };
        SetConsoleCtrlHandler(_consoleCtrlHandler, true);
    }
}

Returning FALSE from the handler tells the framework that we are not "handling" the control signal, and the next handler function in the list of handlers for this process is used. If none of the handlers returns TRUE, the default handler is called.

Note that when the user performs a logoff or shutdown, the callback is not called by Windows but is instead terminated immediately.

Answer 8

Visual Studio 2015 + Windows 10

• Allow for cleanup
• Single instance app
• Some goldplating

Code:

using System;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;

namespace YourNamespace
{
    class Program
    {
        // if you want to allow only one instance otherwise remove the next line
        static Mutex mutex = new Mutex(false, "YOURGUID-YOURGUID-YOURGUID-YO");

        static ManualResetEvent run = new ManualResetEvent(true);

        [DllImport("Kernel32")]
        private static extern bool SetConsoleCtrlHandler(EventHandler handler, bool add);                
        private delegate bool EventHandler(CtrlType sig);
        static EventHandler exitHandler;
        enum CtrlType
        {
            CTRL_C_EVENT = 0,
            CTRL_BREAK_EVENT = 1,
            CTRL_CLOSE_EVENT = 2,
            CTRL_LOGOFF_EVENT = 5,
            CTRL_SHUTDOWN_EVENT = 6
        }
        private static bool ExitHandler(CtrlType sig)
        {
            Console.WriteLine("Shutting down: " + sig.ToString());            
            run.Reset();
            Thread.Sleep(2000);
            return false; // If the function handles the control signal, it should return TRUE. If it returns FALSE, the next handler function in the list of handlers for this process is used (from MSDN).
        }


        static void Main(string[] args)
        {
            // if you want to allow only one instance otherwise remove the next 4 lines
            if (!mutex.WaitOne(TimeSpan.FromSeconds(2), false))
            {
                return; // singleton application already started
            }

            exitHandler += new EventHandler(ExitHandler);
            SetConsoleCtrlHandler(exitHandler, true);

            try
            {
                Console.BackgroundColor = ConsoleColor.Gray;
                Console.ForegroundColor = ConsoleColor.Black;
                Console.Clear();
                Console.SetBufferSize(Console.BufferWidth, 1024);

                Console.Title = "Your Console Title - XYZ";

                // start your threads here
                Thread thread1 = new Thread(new ThreadStart(ThreadFunc1));
                thread1.Start();

                Thread thread2 = new Thread(new ThreadStart(ThreadFunc2));
                thread2.IsBackground = true; // a background thread
                thread2.Start();

                while (run.WaitOne(0))
                {
                    Thread.Sleep(100);
                }

                // do thread syncs here signal them the end so they can clean up or use the manual reset event in them or abort them
                thread1.Abort();
            }
            catch (Exception ex)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.Write("fail: ");
                Console.ForegroundColor = ConsoleColor.Black;
                Console.WriteLine(ex.Message);
                if (ex.InnerException != null)
                {
                    Console.WriteLine("Inner: " + ex.InnerException.Message);
                }
            }
            finally
            {                
                // do app cleanup here

                // if you want to allow only one instance otherwise remove the next line
                mutex.ReleaseMutex();

                // remove this after testing
                Console.Beep(5000, 100);
            }
        }

        public static void ThreadFunc1()
        {
            Console.Write("> ");
            while ((line = Console.ReadLine()) != null)
            {
                if (line == "command 1")
                {

                }
                else if (line == "command 1")
                {

                }
                else if (line == "?")
                {

                }

                Console.Write("> ");
            }
        }


        public static void ThreadFunc2()
        {
            while (run.WaitOne(0))
            {
                Thread.Sleep(100);
            }

           // do thread cleanup here
            Console.Beep();         
        }

    }
}

Answer 9

The link mentioned above by Charle B in comment to flq

Deep down says:

SetConsoleCtrlHandler won't work on windows7 if you link to user32

Some where else in the thread it is suggested to crate a hidden window. So I create a winform and in onload I attached to console and execute original Main. And then SetConsoleCtrlHandle works fine (SetConsoleCtrlHandle is called as suggested by flq)

public partial class App3DummyForm : Form
{
    private readonly string[] _args;

    public App3DummyForm(string[] args)
    {
        _args = args;
        InitializeComponent();
    }

    private void App3DummyForm_Load(object sender, EventArgs e)
    {
        AllocConsole();
        App3.Program.OriginalMain(_args);
    }

    [DllImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool AllocConsole();
}

Answer 10

For those interested in VB.net. (I searched the internet and couldn't find an equivalent for it) Here it is translated into vb.net.

    <DllImport("kernel32")> _
    Private Function SetConsoleCtrlHandler(ByVal HandlerRoutine As HandlerDelegate, ByVal Add As Boolean) As Boolean
    End Function
    Private _handler As HandlerDelegate
    Private Delegate Function HandlerDelegate(ByVal dwControlType As ControlEventType) As Boolean
    Private Function ControlHandler(ByVal controlEvent As ControlEventType) As Boolean
        Select Case controlEvent
            Case ControlEventType.CtrlCEvent, ControlEventType.CtrlCloseEvent
                Console.WriteLine("Closing...")
                Return True
            Case ControlEventType.CtrlLogoffEvent, ControlEventType.CtrlBreakEvent, ControlEventType.CtrlShutdownEvent
                Console.WriteLine("Shutdown Detected")
                Return False
        End Select
    End Function
    Sub Main()
        Try
            _handler = New HandlerDelegate(AddressOf ControlHandler)
            SetConsoleCtrlHandler(_handler, True)
     .....
End Sub