c# - without - windows child process termination

Kill child process when parent process is killed (8)

I'm creating new processes using System.Diagnostics.Process class from my application.

I want this processes to be killed when/if my application has crashed. But if I kill my application from Task Manager, child processes are not killed.

Is there any way to make child processes dependent on parent process?

From this forum, credit to 'Josh'.

Application.Quit() and Process.Kill() are possible solutions, but have proven to be unreliable. When your main application dies, you are still left with child processes running. What we really want is for the child processes to die as soon as the main process dies.

The solution is to use "job objects" http://msdn.microsoft.com/en-us/library/ms682409(VS.85).aspx.

The idea is to create a "job object" for your main application, and register your child processes with the job object. If the main process dies, the OS will take care of terminating the child processes.

public enum JobObjectInfoType
    AssociateCompletionPortInformation = 7,
    BasicLimitInformation = 2,
    BasicUIRestrictions = 4,
    EndOfJobTimeInformation = 6,
    ExtendedLimitInformation = 9,
    SecurityLimitInformation = 5,
    GroupInformation = 11

    public int nLength;
    public IntPtr lpSecurityDescriptor;
    public int bInheritHandle;

    public Int64 PerProcessUserTimeLimit;
    public Int64 PerJobUserTimeLimit;
    public Int16 LimitFlags;
    public UInt32 MinimumWorkingSetSize;
    public UInt32 MaximumWorkingSetSize;
    public Int16 ActiveProcessLimit;
    public Int64 Affinity;
    public Int16 PriorityClass;
    public Int16 SchedulingClass;

    public UInt64 ReadOperationCount;
    public UInt64 WriteOperationCount;
    public UInt64 OtherOperationCount;
    public UInt64 ReadTransferCount;
    public UInt64 WriteTransferCount;
    public UInt64 OtherTransferCount;

    public JOBOBJECT_BASIC_LIMIT_INFORMATION BasicLimitInformation;
    public IO_COUNTERS IoInfo;
    public UInt32 ProcessMemoryLimit;
    public UInt32 JobMemoryLimit;
    public UInt32 PeakProcessMemoryUsed;
    public UInt32 PeakJobMemoryUsed;

public class Job : IDisposable
    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
    static extern IntPtr CreateJobObject(object a, string lpName);

    static extern bool SetInformationJobObject(IntPtr hJob, JobObjectInfoType infoType, IntPtr lpJobObjectInfo, uint cbJobObjectInfoLength);

    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool AssignProcessToJobObject(IntPtr job, IntPtr process);

    private IntPtr m_handle;
    private bool m_disposed = false;

    public Job()
        m_handle = CreateJobObject(null, null);

        info.LimitFlags = 0x2000;

        extendedInfo.BasicLimitInformation = info;

        int length = Marshal.SizeOf(typeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION));
        IntPtr extendedInfoPtr = Marshal.AllocHGlobal(length);
        Marshal.StructureToPtr(extendedInfo, extendedInfoPtr, false);

        if (!SetInformationJobObject(m_handle, JobObjectInfoType.ExtendedLimitInformation, extendedInfoPtr, (uint)length))
            throw new Exception(string.Format("Unable to set information.  Error: {0}", Marshal.GetLastWin32Error()));

    #region IDisposable Members

    public void Dispose()


    private void Dispose(bool disposing)
        if (m_disposed)

        if (disposing) {}

        m_disposed = true;

    public void Close()
        m_handle = IntPtr.Zero;

    public bool AddProcess(IntPtr handle)
        return AssignProcessToJobObject(m_handle, handle);


Looking at the constructor ...

info.LimitFlags = 0x2000;

The key here is to setup the job object properly. In the constructor I'm setting the "limits" to 0x2000, which is the numeric value for JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE.

MSDN defines this flag as:

Causes all processes associated with the job to terminate when the last handle to the job is closed.

Once this class is setup...you just have to register each child process with the job. For example:

[DllImport("user32.dll", SetLastError = true)]
public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

Excel.Application app = new Excel.ApplicationClass();

uint pid = 0;
Win32.GetWindowThreadProcessId(new IntPtr(app.Hwnd), out pid);

Here's an alternative that may work for some when you have control of the code the child process runs. The benefit of this approach is it doesn't require any native Windows calls.

The basic idea is to redirect the child's standard input to a stream whose other end is connected to the parent, and use that stream to detect when the parent has gone away. When you use System.Diagnostics.Process to start the child, it's easy to ensure its standard input is redirected:

Process childProcess = new Process();
childProcess.StartInfo = new ProcessStartInfo("pathToConsoleModeApp.exe");
childProcess.StartInfo.RedirectStandardInput = true;

childProcess.StartInfo.CreateNoWindow = true; // no sense showing an empty black console window which the user can't input into

And then, on the child process, take advantage of the fact that Reads from the standard input stream will always return with at least 1 byte until the stream is closed, when they will start returning 0 bytes. An outline of the way I ended up doing this is below; my way also uses a message pump to keep the main thread available for things other than watching standard in, but this general approach could be used without message pumps too.

using System;
using System.IO;
using System.Threading;
using System.Windows.Forms;

static int Main()
    Application.Run(new MyApplicationContext());
    return 0;

public class MyApplicationContext : ApplicationContext
    private SynchronizationContext _mainThreadMessageQueue = null;
    private Stream _stdInput;

    public MyApplicationContext()
        _stdInput = Console.OpenStandardInput();

        // feel free to use a better way to post to the message loop from here if you know one ;)    
        System.Windows.Forms.Timer handoffToMessageLoopTimer = new System.Windows.Forms.Timer();
        handoffToMessageLoopTimer.Interval = 1;
        handoffToMessageLoopTimer.Tick += new EventHandler((obj, eArgs) => { PostMessageLoopInitialization(handoffToMessageLoopTimer); });

    private void PostMessageLoopInitialization(System.Windows.Forms.Timer t)
        if (_mainThreadMessageQueue == null)
            _mainThreadMessageQueue = SynchronizationContext.Current;

        // constantly monitor standard input on a background thread that will
        // signal the main thread when stuff happens.

        // start up your application's real work here

    private void BeginMonitoringStdIn(object state)
        if (SynchronizationContext.Current == _mainThreadMessageQueue)
            // we're already running on the main thread - proceed.
            var buffer = new byte[128];

            _stdInput.BeginRead(buffer, 0, buffer.Length, (asyncResult) =>
                    int amtRead = _stdInput.EndRead(asyncResult);

                    if (amtRead == 0)
                        _mainThreadMessageQueue.Post(new SendOrPostCallback(ApplicationTeardown), null);
                }, null);
            // not invoked from the main thread - dispatch another call to this method on the main thread and return
            _mainThreadMessageQueue.Post(new SendOrPostCallback(BeginMonitoringStdIn), null);

    private void ApplicationTeardown(object state)
        // tear down your application gracefully here


Caveats to this approach:

  1. the actual child .exe that is launched must be a console application so it remains attached to stdin/out/err. As in the above example, I easily adapted my existing application that used a message pump (but didn't show a GUI) by just creating a tiny console project that referenced the existing project, instantiating my application context and calling Application.Run() inside the Main method of the console .exe.

  2. Technically, this merely signals the child process when the parent exits, so it will work whether the parent process exited normally or crashed, but its still up to the child processes to perform its own shutdown. This may or may not be what you want...

I was looking for a solution to this problem that did not require unmanaged code. I was also not able to use standard input/output redirection because it was a Windows Forms application.

My solution was to create a named pipe in the parent process and then connect the child process to the same pipe. If the parent process exits then the pipe becomes broken and the child can detect this.

Below is an example using two console applications:


private const string PipeName = "471450d6-70db-49dc-94af-09d3f3eba529";

public static void Main(string[] args)
    Console.WriteLine("Main program running");

    using (NamedPipeServerStream pipe = new NamedPipeServerStream(PipeName, PipeDirection.Out))

        Console.WriteLine("Press any key to exit");


private const string PipeName = "471450d6-70db-49dc-94af-09d3f3eba529"; // same as parent

public static void Main(string[] args)
    Console.WriteLine("Child process running");

    using (NamedPipeClientStream pipe = new NamedPipeClientStream(".", PipeName, PipeDirection.In))
        pipe.BeginRead(new byte[1], 0, 1, PipeBrokenCallback, pipe);

        Console.WriteLine("Press any key to exit");

private static void PipeBrokenCallback(IAsyncResult ar)
    // the pipe was closed (parent process died), so exit the child process too

        NamedPipeClientStream pipe = (NamedPipeClientStream)ar.AsyncState;
    catch (IOException) { }


I've made a child process management library where the parent process and the child process are monitored due a bidirectional WCF pipe. If either the child process terminates or the parent process terminates each other is notified. There is also a debugger helper available which automatically attaches the VS debugger to the started child process

Project site:


NuGet Packages:

https://www.nuget.org/packages/ChildProcesses https://www.nuget.org/packages/ChildProcesses.VisualStudioDebug/

One way is to pass PID of parent process to the child. The child will periodically poll if the process with the specified pid exists or not. If not it will just quit.

You can also use Process.WaitForExit method in child method to be notified when the parent process ends but it might not work in case of Task Manager.

There is another relevant method, easy and effective, to finish child processes on program termination. You can implement and attach a debugger to them from the parent; when the parent process ends, child processes will be killed by the OS. It can go both ways attaching a debugger to the parent from the child (note that you can only attach one debugger at a time). You can find more info on the subject here.

Here you have an utility class that launches a new process and attaches a debugger to it. It has been adapted from this post by Roger Knapp. The only requirement is that both processes need to share the same bitness. You cannot debug a 32bit process from a 64bit process or vice versa.

public class ProcessRunner
    #region "API imports"

    private const int DBG_CONTINUE = 0x00010002;
    private const int DBG_EXCEPTION_NOT_HANDLED = unchecked((int) 0x80010001);

    private enum DebugEventType : int
        //Reports a create-process debugging event. The value of u.CreateProcessInfo specifies a CREATE_PROCESS_DEBUG_INFO structure.
        //Reports a create-thread debugging event. The value of u.CreateThread specifies a CREATE_THREAD_DEBUG_INFO structure.
        //Reports an exception debugging event. The value of u.Exception specifies an EXCEPTION_DEBUG_INFO structure.
        //Reports an exit-process debugging event. The value of u.ExitProcess specifies an EXIT_PROCESS_DEBUG_INFO structure.
        //Reports an exit-thread debugging event. The value of u.ExitThread specifies an EXIT_THREAD_DEBUG_INFO structure.
        //Reports a load-dynamic-link-library (DLL) debugging event. The value of u.LoadDll specifies a LOAD_DLL_DEBUG_INFO structure.
        //Reports an output-debugging-string debugging event. The value of u.DebugString specifies an OUTPUT_DEBUG_STRING_INFO structure.
        RIP_EVENT = 9,
        //Reports a RIP-debugging event (system debugging error). The value of u.RipInfo specifies a RIP_INFO structure.
        //Reports an unload-DLL debugging event. The value of u.UnloadDll specifies an UNLOAD_DLL_DEBUG_INFO structure.

    private struct DEBUG_EVENT
        [MarshalAs(UnmanagedType.I4)] public DebugEventType dwDebugEventCode;
        public int dwProcessId;
        public int dwThreadId;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1024)] public byte[] bytes;

    [DllImport("Kernel32.dll", SetLastError = true)]
    private static extern bool DebugActiveProcess(int dwProcessId);

    [DllImport("Kernel32.dll", SetLastError = true)]
    private static extern bool WaitForDebugEvent([Out] out DEBUG_EVENT lpDebugEvent, int dwMilliseconds);

    [DllImport("Kernel32.dll", SetLastError = true)]
    private static extern bool ContinueDebugEvent(int dwProcessId, int dwThreadId, int dwContinueStatus);

    [DllImport("Kernel32.dll", SetLastError = true)]
    public static extern bool IsDebuggerPresent();


    public Process ChildProcess { get; set; }

    public bool StartProcess(string fileName)
        var processStartInfo = new ProcessStartInfo(fileName)
            UseShellExecute = false,
            WindowStyle = ProcessWindowStyle.Normal,
            ErrorDialog = false

        this.ChildProcess = Process.Start(processStartInfo);
        if (ChildProcess == null)
            return false;

        new Thread(NullDebugger) {IsBackground = true}.Start(ChildProcess.Id);
        return true;

    private void NullDebugger(object arg)
        // Attach to the process we provided the thread as an argument
        if (DebugActiveProcess((int) arg))
            var debugEvent = new DEBUG_EVENT {bytes = new byte[1024]};
            while (!this.ChildProcess.HasExited)
                if (WaitForDebugEvent(out debugEvent, 1000))
                    // return DBG_CONTINUE for all events but the exception type
                    var continueFlag = DBG_CONTINUE;
                    if (debugEvent.dwDebugEventCode == DebugEventType.EXCEPTION_DEBUG_EVENT)
                        continueFlag = DBG_EXCEPTION_NOT_HANDLED;
                    ContinueDebugEvent(debugEvent.dwProcessId, debugEvent.dwThreadId, continueFlag);
            //we were not able to attach the debugger
            //do the processes have the same bitness?
            //throw ApplicationException("Unable to attach debugger") // Kill child? // Send Event? // Ignore?


    new ProcessRunner().StartProcess("c:\\Windows\\system32\\calc.exe");

This post is intended as an extension to @Matt Howells' answer, specifically for those who run into problems with using Job Objects under Vista or Win7, especially if you get an access denied error ('5') when calling AssignProcessToJobObject.


To ensure compatibility with Vista and Win7, add the following manifest to the .NET parent process:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <v3:trustInfo xmlns:v3="urn:schemas-microsoft-com:asm.v3">
        <v3:requestedExecutionLevel level="asInvoker" uiAccess="false" />
  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
    <!-- We specify these, in addition to the UAC above, so we avoid Program Compatibility Assistant in Vista and Win7 -->
    <!-- We try to avoid PCA so we can use Windows Job Objects -->
    <!-- See https://.com/questions/3342941/kill-child-process-when-parent-process-is-killed -->

      <!--The ID below indicates application support for Windows Vista -->
      <supportedOS Id="{e2011457-1546-43c5-a5fe-008deee3d3f0}"/>
      <!--The ID below indicates application support for Windows 7 -->
      <supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}"/>

Note that when you add new manifest in Visual Studio 2012 it will contain the above snippet already so you do not need to copy it from hear. It will also include a node for Windows 8.

full explanation

Your job association will fail with an access denied error if the process you're starting is already associated with another job. Enter Program Compatibility Assistant, which, starting in Windows Vista, will assign all kinds of processes to its own jobs.

In Vista you can mark your application to be excluded from PCA by simply including an application manifest. Visual Studio seems to do this for .NET apps automatically, so you're fine there.

A simple manifest no longer cuts it in Win7. [1] There, you have to specifically specify that you're compatible with Win7 with the tag in your manifest. [2]

This led me to worry about Windows 8. Will I have to change my manifest once again? Apparently there's a break in the clouds, as Windows 8 now allows a process to belong to multiple jobs. [3] So I haven't tested it yet, but I imagine that this madness will be over now if you simply include a manifest with the supportedOS information.

Tip 1: If you're developing a .NET app with Visual Studio, as I was, here [4] are some nice instructions on how to customize your application manifest.

Tip 2: Be careful with launching your application from Visual Studio. I found that, after adding the appropriate manifest, I still had problems with PCA when launching from Visual Studio, even if I used Start without Debugging. Launching my application from Explorer worked, however. After manually adding devenv for exclusion from PCA using the registry, starting applications that used Job Objects from VS started working as well. [5]

Tip 3: If you ever want to know if PCA is your problem, try launching your application from the command line, or copy the program to a network drive and run it from there. PCA is automatically disabled in those contexts.

[1] http://blogs.msdn.com/b/cjacks/archive/2009/06/18/pca-changes-for-windows-7-how-to-tell-us-you-are-not-an-installer-take-2-because-we-changed-the-rules-on-you.aspx

[2] http://ayende.com/blog/4360/how-to-opt-out-of-program-compatibility-assistant

[3] http://msdn.microsoft.com/en-us/library/windows/desktop/ms681949(v=vs.85).aspx: "A process can be associated with more than one job in Windows 8"

[4] How can I embed an application manifest into an application using VS2008?

[5] How to stop the Visual Studio debugger starting my process in a job object?

Use event handlers to make hooks on a few exit scenarios:

var process = Process.Start("program.exe");
AppDomain.CurrentDomain.DomainUnload += (s, e) => { process.Kill(); process.WaitForExit(); };
AppDomain.CurrentDomain.ProcessExit += (s, e) => { process.Kill(); process.WaitForExit(); };
AppDomain.CurrentDomain.UnhandledException += (s, e) => { process.Kill(); process.WaitForExit(); };