How do I get a UserControl derived class thats bound to ObservableCollection to respond to adds?

My collection seems fine as I am able to use a ListView and it responds correctly to adds, however when I nest a listview into a UserControl it doesn't. I've provided the pertinent code.

I've created a UserControl derived class in this fashion:

public partial class MyCtrl: UserControl
{
    #region Static Properties

    public static readonly DependencyProperty ItemsSourceProperty =
        ItemsControl.ItemsSourceProperty.AddOwner(
        typeof(MyCtrl),
        new PropertyMetadata(MyCtrl.ItemsSourcePropertyChangedCallback));

    public IEnumerable ItemsSource
    {
        get { return (IEnumerable)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    public static void ItemsSourcePropertyChangedCallback(
        DependencyObject controlInstance,
        DependencyPropertyChangedEventArgs e)
    {
         MyCtrl myInstance=(MyCtrl)controlInstance;
         myInstance.nestedList.ItemsSource=e.NewValue as IEnumerable;
    }
}

With the XAML like this:

<UserControl x:Class="MyCtrl"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microso开发者_如何学JAVAft.com/winfx/2006/xaml">
    <Grid>
        <ListView Name="nestedList" />
    </Grid>
</UserControl>

My consuming XAML looks like this:

<MyCtrl x:Name="myInstance" ItemsSource="{Binding Path=MyCollection}" />

Where the collection is defined like this:

public static readonly DependencyProperty MyCollectionProperty =
       DependencyProperty.Register("MyCollection",
       typeof(ObservableCollection<MyObject>),
       typeof(ConsumingObject),
       new PropertyMetadata(new ObservableCollection<MyObject>());

public ObservableCollection<MyObject> MyCollection
{
    get { return   (ObservableCollection<MyObject>)this.GetValue(MyCollectionProperty); }
    set { this.SetValue(MyCollectionProperty, value); }
}

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maybe you want to register an event handler on CollectionChanged if your ItemSource is an ObservableCollection< T >

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This questions maybe can help. What is the DataContext of myInstance?
Was the code able to go to this line?
myInstance.nestedList.ItemsSource=e.NewValue as IEnumerable;
If yes then is nestedList null or not?