listbox not showing new items - wpf

Question

I have a listbox that i've bound its ItemsSource and SelectedIndex to objects in the ViewModel. I'm also using an extender to auto scroll to the selected item. When I create the list there is some initial data, then I as i move through the list more items are added. The initial data shows up fine and I can scroll through it as I would expect. the problem is that once I add more items the new items don't show up in the listbox. When I move to the new items the list box stops actually scrolling to the selected item, but starts again when I move back. When I look at the ItemsSource in Snoop it shows all of the items, but they aren't displayed. The only items that are display are the original items. So I guess my question is why is this happening?
here is the xaml I'm using for the list box
<ListBox ItemsSource="{Binding Path=Items}"
Width="{Binding Path=Size.SizeW}"
Height="{Binding Path=Size.SizeH}"
SelectedIndex="{Binding Path=FocusedRow, Mode=OneWay}"
ScrollViewer.HorizontalScrollBarVisibility="Hidden"
ScrollViewer.VerticalScrollBarVisibility="Hidden"
IsSynchronizedWithCurrentItem="True"
extenders:ListBoxExtenders.AutoScrollToCurrentItem="True">
<ListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Setter Property="Height"
Value="{Binding Path=RowHeight}" />
<Setter Property="Width"
Value="{Binding Path=RowWidth}" />
<Setter Property="Margin"
Value="{Binding Path=RowSpacing}" />
</Style>
</ListBox.ItemContainerStyle>
<ListBox.ItemTemplate>
<DataTemplate>
<m:CanvasItemsControl ItemTemplateSelector="{StaticResource ResourceKey=listViewItemTemplateSelector}"
Visibility="Visible"
ItemsSource="{Binding Path=ListItems}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas Height="{Binding Path=RowHeight}"
Width="{Binding Path=RowWidth}"
ClipToBounds="True" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</m:CanvasItemsControl>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
here is the code for the extender
public class ListBoxExtenders : DependencyObject
{
public static readonly DependencyProperty AutoScrollToCurrentItemProperty = DependencyProperty.RegisterAttached("AutoScrollToCurrentItem", typeof(bool), typeof(ListBoxExtenders), new UIPropertyMetadata(default(bool), OnAutoScrollToCurrentItemChanged));
public static bool GetAutoScrollToCurrentItem(DependencyObject obj)
{
return (bool)obj.GetValue(AutoScrollToCurrentItemProperty);
}
public static void SetAutoScrollToCurrentItem(DependencyObject obj, bool value)
{
obj.SetValue(AutoScrollToCurrentItemProperty, value);
}
public static void OnAutoScrollToCurrentItemChanged(DependencyObject s, DependencyPropertyChangedEventArgs e)
{
var listBox = s as ListBox;
if (listBox != null)
{
var listBoxItems = listBox.Items;
if (listBoxItems != null)
{
var newValue = (bool)e.NewValue;
var autoScrollToCurrentItemWorker = new EventHandler((s1, e2) => OnAutoScrollToCurrentItem(listBox, listBox.Items.CurrentPosition));
if (newValue)
{ listBoxItems.CurrentChanged += autoScrollToCurrentItemWorker; }
else
{ listBoxItems.CurrentChanged -= autoScrollToCurrentItemWorker; }
}
}
}
public static void OnAutoScrollToCurrentItem(ListBox listBox, int index)
{
if (listBox != null && listBox.Items != null && listBox.Items.Count > index && index >= 0)
{
listBox.ScrollIntoView(listBox.Items[index]);
}
}
}
I'm not sure what other information would be helpful so if there is something else you need to see let me know and I'll add it.
Listbox SelectedIndex is bound to FocusedRow
private uint focusedRow;
public uint FocusedRow
{
get
{ return focusedRow; }
set
{
if (value == focusedRow)
{ return; }
focusedRow = value;
base.RaisePropertyChanged("FocusedRow");
}
}
ItemsSource is bound to Items
private ObservableCollection<DisplayList> items;
public ObservableCollection<DisplayList> Items
{
get
{ return items; }
set
{
if (value == items)
{ return; }
items = value;
base.RaisePropertyChanged("Items");
}
}

Answer 1

Make sure that new items have valid RowHeight and RowWidth. That can be the problem since while snooping you could see your data.

Answer 2

Make sure that your "Items" you bound as ItemsSource of your listbox is an ObservableCollection<> and not a simple List.
it should work !