1.平时工作中用到的
private List<T> GetChildObjects<T>(DependencyObject obj) where T : FrameworkElement
        {
            DependencyObject child = null;
            List<T> childList = new List<T>();
            for (int i = 0; i <= VisualTreeHelper.GetChildrenCount(obj) - 1; i++)
            {
                child = VisualTreeHelper.GetChild(obj, i);
                if (child is T)
                {
                    childList.Add((T)child);
                }
                childList.AddRange(GetChildObjects<T>(child));
            }
            return childList;
        }