CODEWITHSUNDEEP
c#windowsscreenshotlockscreen
Matthias
Matthias

Reputation: 1437

Take screenshot right before Windows locks

I'm just playing around a bit. I try to take a screenshot of the main monitor right before the user locks the machine. So far nothing worked.

I tried a SystemEvents.SessionSwith but the window handler is not valid anymore at that time.

I also tried a LowLevelKeyboardProc to catch Win+L, take the screenshot and then lock the machine myself - but Win+L seems to be a somehow protected shortcut.

This is what I've got so far

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    SystemEvents.SessionSwitch += SystemEvents_SessionSwitch;
}

private void SystemEvents_SessionSwitch(object sender, SessionSwitchEventArgs e)
{
    switch (e.Reason)
    {
        case SessionSwitchReason.SessionLock: TakeScreenShot(); break;
    }
}

private void TakeScreenShot()
{
    var screen = Screen.AllScreens.Single(x => x.Primary);
    var screenshot = new Bitmap(screen.Bounds.Width, screen.Bounds.Height, PixelFormat.Format32bppArgb);
    var gfxScreenshot = Graphics.FromImage(screenshot);
    gfxScreenshot.CopyFromScreen(screen.Bounds.X, screen.Bounds.Y, 0, 0, screen.Bounds.Size, CopyPixelOperation.SourceCopy);
    screenshot.Save("tmp.png");
}

Fails with System.ComponentModel.Win32Exception: 'The handle is invalid'

Upvotes: 1

Views: 135

Answers (1)

Matthias
Matthias

Reputation: 1437

I ended up using my own shortcut (Win+Shift+L) for taking the screenshot and then locking the machine. Thanks @Hans Passant for the hint.

Upvotes: 1

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