public static void ClosePOS()
 {
     if (instance != null)
     {
         instance.Close();
         instance = null;
     }
 }
        public static void ShowPOS()
        {
            instance = new POSView()
            {
                OverlayVisible = Settings.Default.POSViewVisible,
            };

            instance.Show();
        }
        public static void ShowPOS()
        {
            instance = new POSView()
            {
                OverlayVisible   = Settings.Default.POSViewVisible,
                ClickTransparent = Settings.Default.ClickThroughEnabled,
            };

            instance.Show();
        }