/// <summary>
 /// Creates a new controller window, or active the existing one.
 /// </summary>
 public static void create()
 {
     if (theInstance == null)
     {
         theInstance = new VarHeightBuildingController();
     }
     theInstance.Show();
     theInstance.Activate();
 }
 protected override void OnClosing(CancelEventArgs e)
 {
     base.OnClosing(e);
     theInstance = null;
 }