windows phone listbox的点击事件

<ListBox x:Name="listbox1" Margin="6">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="15" Tag="{Binding ImageID}" Tap="Post_Click">
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Image}" Width="150" Height="120" Stretch="Fill"/>
<TextBlock Text="{Binding ImageName}" FontSize="30" TextWrapping="Wrap" Width="300"/>
</StackPanel>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

private T FindFirstElementInVisualTree<T>(DependencyObject parentElement) where T : DependencyObject
{
var count = VisualTreeHelper.GetChildrenCount(parentElement);
if (count == 0)
return null;
for (int i = 0; i < count; i++)
{
var child = VisualTreeHelper.GetChild(parentElement, i);
if (child != null && child is T)
{
return (T)child;
}
else
{
var result = FindFirstElementInVisualTree<T>(child);
if (result != null)
return result;
}
}
return null;
}

private void Post_Click(object sender, System.Windows.Input.GestureEventArgs e)
{
var selectedIndex = listbox1.SelectedIndex;
ListBoxItem item = listbox1.ItemContainerGenerator.ContainerFromIndex(selectedIndex) as ListBoxItem;
StackPanel border = FindFirstElementInVisualTree<StackPanel>(item);
Image img = FindFirstElementInVisualTree<Image>(item);
TextBlock txtBlock = FindFirstElementInVisualTree<TextBlock>(item);
MessageBox.Show(txtBlock.Text.ToString());
}