This .NET class wraps the AcGeRay2d ObjectARX class. It represents a half-bounded line in 2D space. A Ray2d object either has a start point but no endpoint, or has an endpoint but no start point.

Autodesk.AutoCAD.Geometry.Entity2d
    Autodesk.AutoCAD.Geometry.Curve2d
        Autodesk.AutoCAD.Geometry.LinearEntity2d
            Autodesk.AutoCAD.Geometry.Ray2d

Public sealed Class Ray2d
Inherits LinearEntity2d

public sealed class Ray2d : LinearEntity2d;