This .NET class wraps the AcDbDictionaryWithDefault ObjectARX class. 

This class enhances the Dictionary class by adding the concept of a 'default' entry. Each DictionaryWithDefault has an HardPointerId data member that is used to store the object ID of one of its entries. This hard pointer ID is used as the default entry. Get and set methods are provided for accessing this hard pointer.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.DBDictionary
        Autodesk.AutoCAD.DatabaseServices.DictionaryWithDefaultDictionary

Public Class DictionaryWithDefaultDictionary
Inherits DBDictionary

public class DictionaryWithDefaultDictionary : DBDictionary;

ObjectId