This .NET class wraps the AcGeCompositeCurve2d ObjectARX class. 

This class represents a composite curve, which is a single curve that consists of any number of component curves that are connected end-to-end. For instance, a composite curve could consist of four straight line segments that form a square. Each of the component curves must be bounded curves, which means that infinite lines and rays may not be used as component curves of a composite. A composite curve object stores a list of pointers to the component curves. 

The start parameter of a composite is 0.0. The parameter value at the endpoint of the first component curve is the approximate length of the first curve (call this value l1). The parameter value at the endpoint of the second curve is l1 plus the approximate length of the second curve, and so forth.

Autodesk.AutoCAD.Geometry.Entity2d
    Autodesk.AutoCAD.Geometry.Curve2d
        Autodesk.AutoCAD.Geometry.CompositeCurve2d

Public sealed Class CompositeCurve2d
Inherits Curve2d

public sealed class CompositeCurve2d : Curve2d;