Proper inhertance?

In my project I have various classes... call them A, B, C etc...

For class A I needed the ability to store them in a collection... so I made this class (CDocument is A):

VB Code:

Public Class CDocumentCollection : Inherits CollectionBase
 
Public Sub Add(ByVal item As CDocument)
            Me.List.Add(item)
        End Sub
        Public ReadOnly Property Item(ByVal index As Integer) As CDocument
            Get
                Return DirectCast(Me.List.Item(index), CDocument)
            End Get
 
        End Property
 
        Public WriteOnly Property Item(ByVal index As Integer, ByVal Document As CDocument) As CDocument
            Set(ByVal Value As CDocument)
                Me.List.Item(index) = Document
            End Set
        End Property
 
    End Class

Now let's say I need to do the same thing for B... Is the best way to do that is to create another class BCollection and define all the methods like I did above (add, item) but using the type B instead of type A(CDocument in the example code).

I feel like something stinks in my code here...

I feel like I should only need one collection class.. but since the objects to be stored in the collections have different parents... I can't do it with a base class as collection parameter...

Like if I had A-Z objecs.. all inherited from TheGod class.. then I could make a collection class like above using TheGod as parameter type... then all siblings should be accepted without any type conversions... polymorphism...


That is also the reason I made the class above in the first place.. I want it type safe! But is that possible to acieve WITHOUT for objects A-Z create ACollection-ZCollection?



kind regards
Henrik - pposting yet another bizarre OO question...

If you want different kinds of objects in one collection, then you will need to have some common super class, or interface. But that removes type safety. The only way you are going to get close to type safety and allow multiple classes to use the same collection class would probably be to simulate generics.

VB Code:

Imports System.Collections
 
Public Class CollectionClass : Inherits CollectionBase
 
    Private _Type As Type
 
    Public Sub New(ByVal T As Type)
        _Type = T
    End Sub
 
    Public Sub Add(ByVal o As Object)
 
        If o.GetType Is _Type Then
            MyBase.List.Add(o)
        Else
            Throw New InvalidOperationException("Object is not of type " & _Type.Name)
        End If
 
    End Sub
 
End Class

Something like that.