New Post: CollectionControl binding

I must be doing something wrong again with CollectionControls but I can't get it to bind properly.

Using the following code I expected to see the myConstruction.LayerCollection.Count increase after the CollectionControl Add button has been clicked but it doesn't. Note that CollectionControl1.Items.Count does update.
(Counts are displayed hen the cmdCount button is clicked)

The xaml

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="800" Width="525" xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit">
    <Grid>
        <StackPanel>
        <xctk:CollectionControl Height="240"
                                HorizontalAlignment="Left"
                                Name="CollectionControl1"
                                VerticalAlignment="Top"
                                Width="479"
                                >
            <xctk:CollectionControl.Style>
                <Style TargetType="xctk:CollectionControl">
                    <Style.Resources>
                        <Style TargetType="ListBox">
                            <Setter Property="ItemTemplate">
                                <Setter.Value>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding DisplayedName}"
                                            Background="LightGreen" />
                                    </DataTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </Style.Resources>
                </Style>
            </xctk:CollectionControl.Style>


        </xctk:CollectionControl>
 
        <Button Name="cmdCount" Content="MaterialCollection.Count"/>
        </StackPanel>
    </Grid>
</Window>

The model

Class MainWindow
    Public myConstruction As New clsConstruction

    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        CollectionControl1.DataContext = myConstruction.LayerCollection
        CollectionControl1.ItemsSource = myConstruction.LayerCollection
        CollectionControl1.NewItemTypes = New ObservableCollection(Of System.Type)() From {GetType(clsConstruction)}


    End Sub

    Private Sub cmdCount_Click(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles cmdCount.Click
        MsgBox(myConstruction.LayerCollection.Count & CollectionControl1.Items.Count)
    End Sub
End Class

where clsMaterial contains:

Imports System.ComponentModel
Imports System.Collections.ObjectModel

Public Class clsMaterial

    Implements INotifyPropertyChanged

    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Public Sub OnPropertyChanged(ByVal e As PropertyChangedEventArgs)
        If Not PropertyChangedEvent Is Nothing Then
            RaiseEvent PropertyChanged(Me, e)
        End If
    End Sub

    Public myLWEmissivityOut As Double
    Public myLWEmissivityIn As Double
    Public myDisplayedName As String


    Public Sub New()
        myDisplayedName = "DefaultName"
        myLWEmissivityOut = 0.0
        myLWEmissivityIn = 0.0

        'OnPropertyChanged(New PropertyChangedEventArgs("Thickness"))

    End Sub

    Public Sub New( _
           ByVal newDisplayedName As String,
           ByVal newLWEmissivityOut As Double,
           ByVal newLWEmissivityIn As Double)

        myDisplayedName = newDisplayedName
        myLWEmissivityOut = newLWEmissivityOut
        myLWEmissivityIn = newLWEmissivityIn

    End Sub

    Public Property DisplayedName() As String
        Get
            Return myDisplayedName
        End Get
        Set(ByVal value As String)
            myDisplayedName = value
        End Set
    End Property

    Public Property LWEmissivityOut() As Double
        Get
            Return myLWEmissivityOut
        End Get
        Set(ByVal value As Double)
            myLWEmissivityOut = value
        End Set
    End Property


    Public Property LWEmissivityIn() As Double
        Get
            Return myLWEmissivityIn
        End Get
        Set(ByVal value As Double)
            myLWEmissivityIn = value
        End Set
    End Property

End Class

and clsConstruction contains:

Imports System.ComponentModel
Imports System.Collections.ObjectModel
Public Class clsConstruction
    Implements INotifyPropertyChanged

    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Public Sub OnPropertyChanged(ByVal e As PropertyChangedEventArgs)
        If Not PropertyChangedEvent Is Nothing Then
            RaiseEvent PropertyChanged(Me, e)
        End If
    End Sub

    Public myLayerCollection As New ObservableCollection(Of clsMaterial)

    Public Sub New()

        myLayerCollection.Add(New clsMaterial())

    End Sub

    Public Property LayerCollection As ObservableCollection(Of clsMaterial)

        Get
            Return myLayerCollection
        End Get
        Set(value As ObservableCollection(Of clsMaterial))
            myLayerCollection = value
            OnPropertyChanged(New PropertyChangedEventArgs("LayerCollection"))
        End Set
    End Property

End Class

Hopefully this is my final CollectionControl related question!

Any help much appreciated.