This .NET class wraps the AcDbViewportTableRecord ObjectARX class. 

Objects of this class represent viewport arrangements when TILEMODE == 1 within AutoCAD (the ViewportTable and its records are not used when TILEMODE == 0). The ViewportTable (referred to in AutoCAD and DXF documentation as the VPORT table) is the container or owner of objects of this class. 

The ViewportTable is unique in that it can contain multiple ViewportTableRecords with the same name. This is necessary because when a multiple viewport configuration is saved, all viewports in the configuration must share the name, but each viewport has its own ViewportTableRecord created to save the data for that viewport.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.SymbolTableRecord
        Autodesk.AutoCAD.DatabaseServices.AbstractViewTableRecord
            Autodesk.AutoCAD.DatabaseServices.ViewportTableRecord

Public Class ViewportTableRecord
Inherits AbstractViewTableRecord

public class ViewportTableRecord : AbstractViewTableRecord;