manski's blog

WPF crashes on exit

So, I’m working on my WPF application and everything runs fine, but when I close it, I get this error message (together with this doesn’t-say-me-anything stacktrace):

[System.ComponentModel.Win32Exception]	{"Invalid window handle"}
  WindowsBase.dll!MS.Win32.HwndWrapper.DestroyWindow(object args) + 0x11a bytes	
  WindowsBase.dll!MS.Win32.HwndWrapper.Dispose(bool disposing, bool isHwndBeingDestroyed) + 0x8c bytes	
  WindowsBase.dll!MS.Win32.HwndWrapper.Dispose() + 0x14 bytes	
  PresentationCore.dll!System.Windows.Interop.HwndSource.Dispose(bool disposing) + 0x1f6 bytes	
  PresentationCore.dll!System.Windows.Interop.HwndSource.WeakEventDispatcherShutdown.OnShutdownFinished(object sender, System.EventArgs e) + 0x33 bytes	
  WindowsBase.dll!System.Windows.Threading.Dispatcher.ShutdownImplInSecurityContext(object state) + 0x49 bytes	
  mscorlib.dll!System.Threading.ExecutionContext.runTryCode(object userData) + 0x51 bytes	
  mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x6a bytes	
  mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool ignoreSyncCtx) + 0x7e bytes	
  mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x2c bytes	
  WindowsBase.dll!System.Windows.Threading.Dispatcher.ShutdownImpl() + 0x72 bytes	
  WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame) + 0xe1 bytes	
  WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes	
  WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() + 0x4c bytes	
  PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) + 0x17 bytes	
  PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) + 0x6f bytes	
  PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) + 0x26 bytes	
  PresentationFramework.dll!System.Windows.Application.Run() + 0x1b bytes	
  GuideDock.exe!GuideDock.App.Main() + 0x94 bytes
  mscoreei.dll!__CorExeMain@0()  + 0x38 bytes	
  mscoree.dll!748c7f16() 	
  [Frames below may be incorrect and/or missing, no symbols loaded for mscoree.dll]	
  mscoree.dll!748c4de3() 	
  kernel32.dll!@BaseThreadInitThunk@12()  + 0x12 bytes	
  ntdll.dll!___RtlUserThreadStart@8()  + 0x27 bytes	
  ntdll.dll!__RtlUserThreadStart@8()  + 0x1b bytes

This problem seemed to appear only randomly until I figured it out today. The problem can be reproduce by this XAML/C# code (together with a WPF window):

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public partial class MainWindow : Window {
  public MainWindow() {
    InitializeComponent();
 
    this.m_touchCanvas.MouseLeave += (s, e) => CrashAppOnClose();
  }
 
  private void CrashAppOnClose() {
    Window wnd = Window.GetWindow(this.m_touchCanvas);
    // This line throws a Win32Exception with "Ivalid window handle".
    wnd.PointToScreen(new Point());
  }
}

Now, when the user closes the window (without using the mouse; eg. with Alt+F4) while the mouse is still in the window, the call to wnd.PointToScreen() (line 11) results in the Win32Exception above. Unfortunately, the doesn’t seem to be any way to check whether this exception will be thrown – I already tried Window.IsLoaded as suggested here with no luck.

What’s more annoying is that the call to PointToScreen() does not appear in the stacktrace. I can’t even imaging how this is possible. That’s why it took me ages to figure this one out.

Btw: I’d like to send a bug report to Microsoft but they haven’t got my account working in three months.

Download the example project

Updates:

  • The problem only arises on 64-bit Windows system. A correct exception is thrown on 32-bit systems.
  • On 64-bit systems the Win32Exception can’t be caught in a try ... catch block. Both PointToScreen() and the point where the exception is thrown are on the same thread.
  • I’ve managed to create a bug report for this problem.

Solution/Workaround:
Given the 32-bit error message – which reads “This Visual is not connected to a PresentationSource.” – I found a way to circumvent this problem. You need to use PresentationSource.FromVisual like this:

private void CrashAppOnClose() {
  Window wnd = Window.GetWindow(this.m_touchCanvas);
  if (PresentationSource.FromVisual(wnd) != null) {
    wnd.PointToScreen(new Point());
  }
}

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