public static Polyline CircleToPoly(this QuickTransaction tr, Circle c)
{
var r = c.Radius;
new Ellipse();
var top = c.Center.Add(new Vector3d(0, r, 0));
var bottom = c.Center.Add(new Vector3d(0, -r, 0));
var right = c.Center.Add(new Vector3d(r, 0, 0));
var left = c.Center.Add(new Vector3d(-r, 0, 0));
var right_cir = new CircularArc3d(bottom, right, top);
var left_cir = new CircularArc3d(top, left, bottom);
var poly = new Polyline();
poly.AddVertexAt(0, new Point2d(right_cir.StartPoint.X, right_cir.StartPoint.Y), right_cir.GetArcBulge(), 0, 0);
poly.AddVertexAt(1, new Point2d(right_cir.EndPoint.X, right_cir.EndPoint.Y), 0, 0, 0);
poly.AddVertexAt(2, new Point2d(left_cir.StartPoint.X, left_cir.StartPoint.Y), left_cir.GetArcBulge(), 0, 0);
poly.AddVertexAt(3, new Point2d(left_cir.EndPoint.X, left_cir.EndPoint.Y), 0, 0, 0);
poly.LayerId = c.LayerId;
tr.BlockTableRecordCurrentSpace.AppendEntity(poly);
tr.AddNewlyCreatedDBObject(poly, true);
c.Erase();
return(poly);
}