This .NET class wraps the AcDb2dVertex ObjectARX class. 

The 2dVertex class represents the vertices in 2D polylines. It is the only ObjectARX API entity that still passes its position in OCS. This is because the Z coordinate is kept in its owning 2dPolyline for historical purposes. If you are not working in two dimensions, it may be better to use an 3dPolyline, or an AcDbSpline. 

Warning

• Do not derive from this class. Attempting to do so will cause your application to halt AutoCAD.
• 2dVertex objects contain the AcDbEntity methods to set the entity properties such as color, layer, and linetype. However, vertices are subentities that must have the same entity properties as the parent polyline. Therefore, using the Entity methods within the AcDb2dVertex objects to change these properties to values other than those of the parent will result in corrupt vertices. An audit can fix those corrupt vertices.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Vertex
            Autodesk.AutoCAD.DatabaseServices.Vertex2d

Public Class Vertex2d
Inherits Vertex

public class Vertex2d : Vertex;