private bool ctrl = false;
        private void MainWindow_KeyUp(object sender, KeyEventArgs args)
        {
            if (args.Key == Key.Escape)
                new Messaging.Message(2, "Window", "LogIn"); // sets content of MainWindow to LogInScreen.
            if (args.Key == Key.LeftCtrl || args.Key == Key.RightCtrl)
                ctrl = true;
            if (args.Key == Key.F && ctrl)
            {
                ctrl = false;
                if (this.WindowStyle == WindowStyle.SingleBorderWindow)
                    this.WindowStyle = WindowStyle.ThreeDBorderWindow;
                else
                    this.WindowStyle = WindowStyle.SingleBorderWindow;;
            }
            args.Handled = true;
        }