public static void ShowSplashScreen()
 {
     if (sf == null)
     {
         sf = new SplashScreenForm();
         sf.ShowSplashScreen();
     }
 }
 public static void CloseSplashScreen()
 {
     if (sf != null)
     {
         sf.CloseSplashScreen();
         sf = null;
     }
 }