This .NET class wraps the AcDbPlaneSurface ObjectARX class. 

This class represents a plane surface entity. It provides methods to create and manipulate ASM surfaces.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Surface
            Autodesk.AutoCAD.DatabaseServices.PlaneSurface

Public Class PlaneSurface
Inherits Surface

public class PlaneSurface : Surface;