I am interested in hearing your opinion on the approach I have taken to have inherited classes initialize their base class.

Here's a Machines collection class from that maintains a list of Machine objects. Each Machine needs to be able to inform its parent, using a delegate, of something they do but they do not have a reference to the parent:

Public Delegate Sub MachineDelegate(ByRef item As Machine)

Public MustInherit Class Machines

    Private _items As New List(Of Machine)

    Public Function Create() As Machine
        Dim item As Machine = CreateItem()
        Return item
    End Function

    ' Create derived object
    Public MustOverride Function CreateItem() As Machine

    Public Sub ChildMachineDidSomething(ByRef item As Machine)
        ' Handle child object event
        Debug.Print("Machine did something")
    End Sub

    ' Called once object has been created
    Protected Overridable Sub PostCreationHandler(ByRef item As Machine)
        item.MachineDelegate = AddressOf ChildMachineDidSomething
    End Sub

End Class

Public Class Machine
    Public MachineDelegate As MachineDelegate

    Public Sub DoMachineThing()
        If Not MachineDelegate Is Nothing Then MachineDelegate(Me)
    End Sub

End Class

The child objects will use a MachineDelegate to inform their parent, passing themselves as a reference.

Inherited Cars and Car classes would look like this and have their own delegate to handle Car-related notifications:

Public Delegate Sub CarDelegate(ByRef item As Car)

Public Class Cars
    Inherits Machines

    ' Create derived object
    Public Overrides Function CreateItem() As Machine
        Dim item As Car = New Car
        CreateItem = item
    End Function

    Public Sub ChildCarDidSomething(ByRef item As Car)
        ' Handle child object event
        Debug.Print("Car did something")
    End Sub

    ' Called once object has been created
    Protected Overrides Sub PostCreationHandler(ByRef item As Machine)
        Dim car As Car = item


        car.CarDelegate = AddressOf ChildCarDidSomething

    End Sub

End Class

Public Class Car
    Inherits Machine

    Public CarDelegate As CarDelegate

    Public Sub DoCarThing()
        If Not CarDelegate Is Nothing Then CarDelegate(Me)
    End Sub

End Class

I create an overridable PostCreationHandler where object-specific initialization is to be handled once an object is created and I am using MyBase.PostCreationHandler to make sure the object gets properly initialized at every level in the inheritance chain.

My goal is to avoid giving child objects a reference to their parent.

My question is is this OK and is there a better approach to doing this?