Determining if a form is completely off screen

Check with this function if Form is fully on screen:

public bool IsOnScreen( Form form )
{
   Screen[] screens = Screen.AllScreens;
   foreach( Screen screen in screens )
   {
      Rectangle formRectangle = new Rectangle( form.Left, form.Top, 
                                               form.Width, form.Height );

      if( screen.WorkingArea.Contains( formRectangle ) )
      {
         return true;
      }
   }

   return false;
}

Checking only top left point if it’s on screen:

public bool IsOnScreen( Form form )
{
   Screen[] screens = Screen.AllScreens;
   foreach( Screen screen in screens )
   {
      Point formTopLeft = new Point( form.Left, form.Top );

      if( screen.WorkingArea.Contains( formTopLeft ) )
      {
         return true;
      }
   }

   return false;
}