This is the base class for a selected object.

Autodesk.AutoCAD.EditorInput.SelectedObject
    Autodesk.AutoCAD.EditorInput.CrossingOrWindowSelectedObject
    Autodesk.AutoCAD.EditorInput.FenceSelectedObject
    Autodesk.AutoCAD.EditorInput.PickPointSelectedObject

Public Class SelectedObject

public class SelectedObject;