public class HierarchicalCollection<T> :
    Collection<T>,
    IHierarchicalEnumerable,
    IEnumerable
    where T : CollectionItem, IHierarchyData

Public Class HierarchicalCollection(Of T As {CollectionItem, IHierarchyData})
    Inherits Collection(Of T)
    Implements IHierarchicalEnumerable,
               IEnumerable