private void Window_KeyDown(object sender, KeyEventArgs e) { bool isLeftAltDown = Keyboard.IsKeyDown(Key.LeftAlt); bool isDeleteDown = Keyboard.IsKeyDown(Key.Delete) || Keyboard.IsKeyDown(Key.Back); if (isLeftAltDown && isDeleteDown) { if (_contributionReport != null) { _contributionReport.Cancel(); } var window = Window.GetWindow(this); if (window != null) { window.KeyDown -= Window_KeyDown; } } }