public override SketchPlane SketchPlane { get; set; }

Public Overrides Property SketchPlane As SketchPlane
	Get
	Set

public:
virtual property SketchPlane^ SketchPlane {
	SketchPlane^ get () override;
	void set (SketchPlane^ value) override;
}

CurveByPoints has no associated SketchPlane. Getting this property returns nullNothingnullptra null reference (Nothing in Visual Basic). Setting it causes an InvalidOperationException.