private static void OnAppDomainProcessExit()
{
// AppDomain is exiting -- if anyone tries to call back into managed code
// after this point, bad things will happen. We must remove all unmanaged
// code references to our WndProc delegates. USER will explode if we set the
// WndProc to null, so the next most reasonable thing we can do is hook up
// the DefaultWindowProc.
//DbgUserBreakPoint();
_exiting = true;
lock (_hwndList)
{
new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert(); // BlessedAssert:
try
{
foreach (DictionaryEntry entry in _hwndList)
{
IntPtr hwnd = (IntPtr)entry.Value;
int windowStyle = UnsafeNativeMethods.GetWindowLong(new HandleRef(null, hwnd), NativeMethods.GWL_STYLE);
if ((windowStyle & NativeMethods.WS_CHILD) != 0)
{
// Tell all the HwndSubclass WndProcs for WS_CHILD windows
// to detach themselves. This is particularly important when
// the parent hwnd belongs to a separate AppDomain in a
// cross AppDomain hosting scenario. In this scenario it is
// possible that the host has subclassed the WS_CHILD window
// and hence it is important to notify the host before we set the
// WndProc to DefWndProc. Also note that we do not want to make a
// blocking SendMessage call to all the subclassed Hwnds in the
// AppDomain because this can lead to slow shutdown speed.
// Eg. Consider a MessageOnlyHwnd created and subclassed on a
// worker thread which is no longer responsive. The SendMessage
// call in this case will block. To avoid this we limit the conversation
// only to WS_CHILD windows. We understand that this solution is
// not foolproof but it is the best outside of re-designing the cleanup
// of Hwnd subclasses.
UnsafeNativeMethods.SendMessage(hwnd, HwndSubclass.DetachMessage,
IntPtr.Zero /* wildcard */,
(IntPtr)2 /* force and forward */);
}
// the last WndProc on the chain might be managed as well
// (see HwndSubclass.SubclassWndProc for explanation).
// Just in case, restore the DefaultWindowProc.
HookUpDefWindowProc(hwnd);
}
}
finally
{
CodeAccessPermission.RevertAssert();
}
}
}
internal static Int32 GetWindowStyle(HandleRef hWnd, bool exStyle)
{
int nIndex = exStyle ? NativeMethods.GWL_EXSTYLE : NativeMethods.GWL_STYLE;
return(UnsafeNativeMethods.GetWindowLong(hWnd, nIndex));
}