public static void RemoveFromHolder(AdvanceSelectable nSelectable)
 {
     if (nSelectables.Contains(nSelectable))
     {
         nSelectables.Remove(nSelectable);
     }
 }
 public static void AddToHolder(AdvanceSelectable nSelectable)
 {
     if (!nSelectables.Contains(nSelectable))
     {
         nSelectables.Add(nSelectable);
     }
 }