How can I override WndProc in WPF? When my window close, I try to check if the file i'm using was modified, if so, I have to promt the user for "Do you want to save changes?" message, then close the file being used and the window.However, I cannot handle the case when user restarts/shutdown/logoff when my window is still open.I cannot override WndProc since I am developing using WPF.I have also tried using this sample MSDN code.This is what I did private void loadedForm(object sender, RoutedEventArgs e) {
HwndSource source = HwndSource.FromHwnd(new WindowInteropHelper(this).Handle);
source.AddHook(new HwndSourceHook(WndProc));
}
private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
if (msg == WM_QUERYENDSESION.)
{
OnWindowClose(this, new CancelEventArgs())
handled = true;
shutdown = true;
}
return IntPtr.Zero;
}
private void OnWindowClose(object sender, CancelEvetArgs e)
{
if (modified)
{
//show message box
//if result is yes/no
e.cancel = false;
//if cancel
e.cancel = true;
}
}
On the XAML file, I also used Closing = "OnWindowClose" however nothing happens when I click yes/no, my application does not close. and if I try to close it again using the close button, I receive an error? why is this so? is it because of the Hook??
What is the equivalent of this in WPF?
private static int WM_QUERYENDSESSION = 0x11;
private static bool systemShutdown = false;
protected override void WndProc(ref System.Windows.Forms.Message m)
{
if (m.Msg==WM_QUERYENDSESSION)
{
systemShutdown = true;
}
// If this is WM_QUERYENDSESSION, the closing event should be
// raised in the base WndProc.
base.WndProc(m);
} //WndProc
private void Form1_Closing(
System.Object sender,
System.ComponentModel.CancelEventArgs e)
{
if (systemShutdown)
// Reset the variable because the user might cancel the
// shutdown.
{
systemShutdown = false;
if (DialogResult.Yes==MessageBox.Show("My application",
"Do you want to save your work before logging off?",
MessageBoxButtons.YesNo))
{
SaveFile();
e.Cancel = false;
}
else{
e.Cancel = true;
}
CloseFile();
}
}