PolyCurve
public static PolyCurve[] ByGroupedCurves(IEnumerable<Curve> curves, double joinTolerance = 0.001, bool trimCurves = false, double trimLength = 0)
public static PolyCurve ByJoinedCurves(IEnumerable<Curve> curves, double joinTolerance = 0.001, bool trimCurves = false, double trimLength = 0)
public PolyCurve ExtendWithEllipse(double length, double radius1, double radius2, double endEllipseParameter, bool endOrStart)