备份一个迭代查找TreeViewItem的辅助函数

private TreeViewItem FindTreeItem(TreeViewItem item, Func<TreeViewItem, bool> compare)
        {
            if (item == null)
            {
                return null;
            }
            var pd = compare?.Invoke(item);//执行比较
            if (pd.HasValue && pd.Value)
            {
                return item;
            }
            if (item.ItemContainerGenerator.Status != System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated)
            {
                item.UpdateLayout();
            }
            for (int i = 0, length = item.Items.Count; i < length; i++)
            {
                var treeitem = FindTreeItem(item.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem, compare);
                if (treeitem != null)
                {
                    return treeitem;
                }
            }
            return null;
        }