Windows Phone 长按ListBox出菜单，获取Item内容，以及Item的Index

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
                <ListBox Height="607" HorizontalAlignment="Left" Margin="-4,0,0,0" Name="listBox1" VerticalAlignment="Top" Width="460" SelectionChanged="listBox1_SelectionChanged" Tap="listBox1_Tap">
                  <toolkit:GestureService.GestureListener>
                        <toolkit:GestureListener Hold="ListItem_Hold"/>
                    </toolkit:GestureService.GestureListener>
                    <toolkit:ContextMenuService.ContextMenu>
                        <toolkit:ContextMenu
                                    Width="200"
                                    BorderBrush="Red"
                                    BorderThickness="5" Background="Chocolate">
                            <toolkit:MenuItem Header="编辑帖子" Click="MenuItemFirst_Click"/>
                            <toolkit:MenuItem Header="删除帖子" />
                            <toolkit:Separator/>
                            <toolkit:MenuItem Header="查看资料"  />
                        </toolkit:ContextMenu>
                    </toolkit:ContextMenuService.ContextMenu> 
            </ListBox>
        </Grid>
    </Grid>

private void ListItem_Hold(object sender, Microsoft.Phone.Controls.GestureEventArgs e)
{
     //第一种实现方法（获取到的zhi+1）
   IEnumerable<UIElement> hits = VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(LayoutRoot), listBox1);
    ListBoxItem item;
    int index = -1;
    foreach (UIElement element in hits)
    {
         if (element is ListBoxItem)
         {
             item = (ListBoxItem)element;
             index =  listBox1.Items.IndexOf(item.Content);
         }
    }
    MessageBox.Show("Currently hovering over item index " + index.ToString());
}