Is Windows Shutting Down

[OBRon]

Is there a way I can check to see if the OS is getting shut down within my application? I have overridden the Closing method to hide my application on the tray; much like what the MSN Messenger does. You hit the X on the system menu and my Closing method sets the e.Cancel to true, sets my WindowState to Minimized and Visibility to false. This all works great; until you attempt a Windows shutdown. My e.Cancel seems to tell the OS that it can't stop. If there is a way for me to determine that the OS is calling my Closing method, then I could leave the e.Cancel alone. Any ideas? Ron Ward

[Richard Deeming]

YeahIGotDotNet posted the code in the VB.NET forum on GotDotNet: http://www.gotdotnet.com/Community/MessageBoard/Thread.aspx?id=40651&Page=1[^] It needs a slight modification, since you're overriding the OnClosing method, rather than attaching to the Closing event, and to include the extra cases further down the same discussion:

using System.Diagnostics;
...
protected override void OnClosing(CancelEventArgs e)
{
base.OnClosing(e);

StackTrace t = new StackTrace(false);

// NB: If you override, you need frame 6.
// If you handle the event, you need frame 7.
StackFrame f = t.GetFrame(**6**);

switch (f.GetMethod().Name) 
{
    case "CallWindowProc":
        // System menu, or the close button
    case "DefMDIChildProc":
        // MDI Child System Menu or close button
    case "DefFrameProc":
        // MDI Parent Closing
    case "ShowDialog":
        // Modal Dialog Closing
    case "DispatchMessageW":
    case "DispatchMessageA":
        // Task manager
    case "SendMessage":
        // Call in code
    default:
        //Don't know
        break;
}

}

I would assume that system shutdown would be the same as the task manager option, but you may want to log the method name just to make sure.

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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[Gaul]

When the user initiates a shutdown, or when the OS is is about to shutdown, Windows sends out the WM_QUERYENDSESSION to all top level applications. Applications should return a non-zero to allow the the shutdown to continue. If any application returns zero, the session is not ended. The system stops sending WM_QUERYENDSESSION messages as soon as one application returns zero. You could override the WndProc (Window Procedure) for you main form, and watch for the WM_QUERYENDSESSION message. public enum Msg { WM_QUERYENDSESSION = 0x0011, WM_QUIT = 0x0012, WM_ENDSESSION = 0x0016, } protected override void WndProc(ref Message m) { switch(m.Msg) { case (int)Msg.WM_QUERYENDSESSION: // your code to handle the end session or respond to it break; default: base.WndProc(ref m); break; } } Gaulles http://www.gaulles.com

[OBRon]

Checking for the WM_QUERYENDSESSION and WM_ENDSESSION worked perfectly! Thanks Gaul.