WPF - ListBox Items collection being emptied

[dlarkin77]

Hi,

I have a user control that is essentially a listbox.
The listbox is bound to a list of objects.
I am using an ItemTemplateSelector to control how each item is displayed.
In one template I am using a Hyperlink.

My problem is as follows:
Whenever I click the hyperlink the listbox's items collection seems to be emptied out.
I can still see the listbox items but if I query myListBox.Items.Count I always get 0.

Is there a reason this should happen?

Thanks,

dlarkin77

This is the DataTemplate that I am using:

<DataTemplate x:Key="NonEPOSCall">
	<Grid Margin="0" Background="White">
		<Border 
			Margin="5" 
			BorderThickness="1" 
			BorderBrush="SteelBlue"
			Background="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}, Path=Background}" 
			CornerRadius="4">
			<Grid Margin="3" Style="{StaticResource GridStyle}">
				<Grid.ColumnDefinitions>
					<ColumnDefinition Width="Auto"></ColumnDefinition>
					<ColumnDefinition Width="*"></ColumnDefinition>
				</Grid.ColumnDefinitions>
				<Grid Grid.Column="1" HorizontalAlignment="Left" ShowGridLines="False">
					<Grid.RowDefinitions>
						<RowDefinition></RowDefinition>
					</Grid.RowDefinitions>
					<Grid.ColumnDefinitions>
						<ColumnDefinition SharedSizeGroup="FirstColumn"></ColumnDefinition>
						<ColumnDefinition SharedSizeGroup="SecondColumn"></ColumnDefinition>
					</Grid.ColumnDefinitions>
					<StackPanel Grid.Row="0" Grid.Column="0" Orientation="Horizontal" VerticalAlignment="Center">
						<TextBlock Text="Account Number:" Margin="3"></TextBlock>
						<TextBlock FontWeight="Bold" Margin="3" Text="{Binding Path=AccountNumber}"></TextBlock>
					</StackPanel>
					<StackPanel Grid.Row="0" Grid.Column="1" Orientation="Horizontal" VerticalAlignment="Center">
						<TextBlock Margin="100,3,3,3">
							<Hyperlink 
								Style="{StaticResource HyperlinkStyle}"
								Click="Hyperlink_Click">
								Next Call Date:
							</Hyperlink>
						</TextBlock>
						<TextBlock FontWeight="Bold" Tag="tbNextCallDate" Margin="20,3,3,3" Text="{Binding Path=NextCallDate}" VerticalAlignment="Center"></TextBlock>
					</StackPanel>
				</Grid>
			</Grid>
		</Border>
	</Grid>
</DataTemplate>

This is how I fill the listbox:

List<CallListItem> items = new List<CallListItem> {  
	new CallListItem { AccountNumber = "456", EPOS = false }, 
	new CallListItem { AccountNumber = "789", EPOS = false } 
};

// callListBox1 is the user control
// lstCalls is the name of the listbox in callListBox1
callListBox1.lstCalls.ItemsSource = items;

Edit: I've attached a sample application showing the behaviour inquestion. You'll need VS 2008 to open it