问longListSelector get索引

EN

        <DataTemplate x:Key="AddrBookItemTemplate" >
            <StackPanel VerticalAlignment="Top">
                <Grid Background="#3FCDCDCD" Margin="3,3,3,3">
                    <Image Source ="{Binding UrlImage}" Height="100" Width="100" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="0,0,0,0" Stretch="Fill"/>
                    <TextBlock Text="{Binding Title}" TextWrapping="Wrap" Margin="110,0,0,0" Foreground="Black" FontFamily="Portable User Interface"/>
                </Grid>
            </StackPanel>
        </DataTemplate>

    </phone:PhoneApplicationPage.Resources>

<phone:LongListSelector
  x:Name="AddrBook"
  Background="Transparent"
  ItemTemplate="{StaticResource AddrBookItemTemplate}"
  IsGroupingEnabled="true"
  HideEmptyGroups ="true"
  SelectionChanged="AddrBook_SelectionChanged"
                    />

 private void AddrBook_SelectionChanged(object sender, SelectionChangedEventArgs e)
        { }