public void OnDeserialization(object sender)
{
region = PdnRegion.CreateEmpty();
Rectangle[] rects = new Rectangle[placedSurfaces.Count];
for (int i = 0; i < placedSurfaces.Count; ++i)
{
rects[i] = ((PlacedSurface)placedSurfaces[i]).Bounds;
}
region = Utility.RectanglesToRegion(rects);
}