This .NET class wraps the AcDbPolyFaceMeshVertex ObjectARX class. 

The PolyFaceMeshVertex class represents the vertices within PolyFaceMesh entities in AutoCAD drawings.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Vertex
            Autodesk.AutoCAD.DatabaseServices.PolyFaceMeshVertex

Public Class PolyFaceMeshVertex
Inherits Vertex

public class PolyFaceMeshVertex : Vertex;

Do not derive from this class. Attempting to do so will cause your application to halt AutoCAD. PolyFaceMeshVertex objects contain the Entity methods to set the entity properties such as color, layer, and linetype, but vertices are subentities that are supposed to have the same entity properties as the parent polyface mesh. So, using the Entity methods within the PolyFaceMeshVertex objects to change these properties to values other than those of the parent results in corrupt vertices (which audit can fix).

PolyFaceMesh