private void StackPanel_Tap(object sender, TappedRoutedEventArgs e)
    {
         //获取到的对象是ListBoxItem
         ListBoxItem myListBoxItem =  (ListBoxItem)(listbox.ItemContainerGenerator.ContainerFromItem((sender as Panel).DataContext));
         // 在ListBoxItem中查找ContentPresenter
         ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(myListBoxItem);
        ……//省略若干代码
    }
    //查找可视化树某个类型的元素
    private childItem FindVisualChild<childItem>(DependencyObject obj) where childItem : DependencyObject
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(obj, i);
            if (child != null && child is childItem)
                return (childItem)child;
            else
            {
                childItem childOfChild = FindVisualChild<childItem>(child);
                if (childOfChild != null)
                    return childOfChild;
            }
        }
        return null;
    }

Windows Phone 中查找可视化树中的某个类型的元素