Design curves

Design curves are what the end user refers to as sketch curves. They're called design curves in the API for consistency with design bodies, design faces, and design edges.

A DesignCurve is a doc object, which has a trimmed curve Shape.

public static void Example(Part part) {
	Line line = Line.Create(Point.Origin, Direction.DirX);
	ITrimmedCurve shape = CurveSegment.Create(line, Interval.Create(-0.01, 0.01));

	// create a design curve
	DesignCurve desCurve = DesignCurve.Create(part, Plane.PlaneXY, shape);

	// the Shape property returns the trimmed curve
	Debug.Assert(Accuracy.EqualLengths(desCurve.Shape.Length, 0.02));

	// override the layer color
	desCurve.SetColor(null, Color.DarkSalmon);
}

A design curve has other properties that are outside the concept of a trimmed curve, such as layer, color override, and name.