根據控件名字，找到控件的子控件

 private FrameworkElement FindByName(string name, FrameworkElement root)
        {
            Stack<FrameworkElement> tree = new Stack<FrameworkElement>();
            tree.Push(root);

            while (tree.Count > 0)
            {
                FrameworkElement current = tree.Pop();
                if (current.Name == name)
                    return current;

                int count = VisualTreeHelper.GetChildrenCount(current);
                for (int i = 0; i < count; ++i)
                {
                    DependencyObject child = VisualTreeHelper.GetChild(current, i);
                    if (child is FrameworkElement)
                        tree.Push((FrameworkElement)child);
                }
            }

            return null;
        }