public void Del(GeometricFigure name)
 {
     foreach (var element in ui)
     {
         int position = 0;
         if (element == name)
         {
             ui.RemoveAt(position);
             break;
         }
         position++;
     }
 }
 public void add(GeometricFigure name)
 {
     ui.Add(name);
 }