C# App using Windows API Code Pack Shell Extension won't shut down

Question

I have a C# application which makes use of the Microsoft Windows API Code Pack - in particular the Shell Extensions, which I use to monitor storage devices and media insertion and removal.

However when I attempt to close the app in Visual C# 2010 (Express) I then have to manually stop the debugger. It appears that there is a background loop in the Win API Code Pack that is still running, even when I manually dispose of the ShellObjectWatcher. The only way I can kill it is to manually stop the debugger.

The app is built in WPF.

Eventually, VisC#2010 gives up on trying to run the app under the debugger. You tell it to start debugging and it just doesn't. Only way to get it going again is to kill the app using Task Manager and then shutdown VC#2010 - go have a coffee - then start it up again. Odd. I suspect there is a hidden process or window hanging around which isn't being shut down when I try and clean up the app.

Any idea how I can clean up this ShellObjectWatcher a little more effectively?

I don't see a "ShellObjectWatcher" class, what version? Shell interfaces invariably have COM threading affinity, be sure to use them only from an [STAThread] in a WPF or Winforms app. If you don't then COM will start a thread to give the object a thread-safe home. — Hans Passant, Feb 15 '12 at 14:20
Its part of the Windows API Code Pack 1.1 It seems to be hanging on a messagelistener thread method inside the code pack. — Mark, Feb 15 '12 at 15:41
I just ran into this as well. Specifically, MessageListener.ThreadMethod() has a blocking call inside a while(_running), so it won't respond if Dispose() tried to end the thread by setting _running. Which, of course, it doesn't. So these MessageListener threads never get cleaned up. This would be fine if it were a background thread, but it isn't. You can see the same behavior on MSFT's own ShellObjectWatcherSampleWPF. — MNGwinn, Sep 14 '12 at 16:15

score 2 · Accepted Answer · edited May 24 '13 at 20:43

2

To fix the bug in the Code Pack Shell project, add one line in MessageListener.WndProc():

case (uint)WindowMessage.Destroy:
 **_running = false;**
 break;

Now ThreadMethod() will exit the message loop.

edited May 24 '13 at 20:43

Matthew Strawbridge

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answered May 24 '13 at 20:25

OrlandoCurioso

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score 1 · Answer 2 · edited Feb 17 '12 at 08:32

1

OK using System.Environment.Exit(0); fixes this issue. App shuts down and the debugger releases control. Brute force works in this case.

edited Feb 17 '12 at 08:32

Aliaksei Kliuchnikau

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answered Feb 17 '12 at 07:45

Mark

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score 0 · Answer 3 · answered Dec 10 '13 at 13:09

I bumped into the same issue, but solved it by setting the thread as a background thread (meaning, it is killed when the application stops):

in MessageListener.cs, in the constructor, at line 40, I have:

_windowThread = new Thread(ThreadMethod);
// The line below will force the thread to terminate when the app exits.
_windowThread.IsBackground = true;
_windowThread.SetApartmentState(ApartmentState.STA);

C# App using Windows API Code Pack Shell Extension won't shut down

3 Answers3