public static Polyline ConvertToPolyline(this QuickTransaction tr, Entity id) { switch (id) { case Polyline poly: return(poly); case Line line: return(LineToPoly(tr, line)); case Arc arc: return(ArcToPoly(tr, arc)); case Circle c: return(CircleToPoly(tr, c)); case Spline sp: return(SplineToPoly(tr, sp)); case Polyline2d p2d: return(ConvertToPolyline(p2d, tr)); default: tr.WriteLine("Unsupported to polyline conversion: " + id.GetType().FullName); return(null); } }