WP8 ContextMenu in Listbox not showing

Question

I got a horizontal ListBox displaying pictures. I wanted to add a ContextMenu on each item allowing the user to delete the item. But I don't know exactly where to put my ContextMenu in my ItemTemplate, I tried approximately everywhere but the ContextMenu never shows on Holding. Do you have an idea where to place the XAML bloc?

<ListBox x:Name="PhotoListBox" Grid.Row="1" ItemsSource="{Binding}" SelectionChanged="PhotoListBox_SelectionChanged" >
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <toolkit:WrapPanel 
                        HorizontalAlignment="Left" 
                        Margin="0,0,0,0" 
                        VerticalAlignment="Top" 
                            />
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Margin="5">
                        <StackPanel Orientation="Vertical">
                            <Grid Width="100" Height="100">
                                <Grid.Background>
                                    <ImageBrush Stretch="UniformToFill" ImageSource="{Binding}" />
                                </Grid.Background>
                                <toolkit:ContextMenu>
                                    <toolkit:MenuItem Header="Delete" Click="MenuItem_OnClick"/>
                                </toolkit:ContextMenu>
                            </Grid>
                        </StackPanel>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

Thanks

Answer 1

wrap it in within the contextMenuService:

<toolkit:ContextMenuService.ContextMenu>
  <toolkit:ContextMenu>
    <toolkit:MenuItem Header="Delete" Click="MenuItem_OnClick"/>
  </toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>

see http://phone.codeplex.com/SourceControl/latest#PhoneToolkitSample/Samples/ContextMenuSample.xaml for a complete sample