简易文件夹无限级，使用递归重构层级列表

 1      /// <summary>
     /// 文件夹实体
     /// </summary>
     public class Folder
     {
         /// <summary>
         /// 文件夹ID
         /// </summary>
         public int id { get; set; }
         /// <summary>
         /// 文件夹名称
         /// </summary>
         public string name { get; set; }
         /// <summary>
         /// 父级ID
         /// </summary>
         public int folder_parent_id { get; set; }
    }

        /// <summary>
        /// 重构文件夹层级列表
        /// </summary>
        /// <param name="listSource">源数据</param>
        /// <param name="pId">父级ID</param>
        /// <param name="count">添加元素的次数</param>
        /// <param name="levelNum">当前层级</param>
        /// <param name="listResult">返回结果集</param>
        private void RefactorFolderLevelList(List<Folder> listSource, int pId, int count, List<int> levelNum, List<Folder> listResult)
        {
            var len_source = listSource.Count();
            if (count < len_source)
            {
                var tmp_list = listSource.Where(m => m.folder_parent_id == pId);
                var len_tmp_list = tmp_list.Count();
                bool addFlag = true;
                int level = levelNum.Count();
                int i = 0;
                foreach (var item in tmp_list)
                {
                    i++;
                    item.name = FillString(level, "——") + item.name;
                    var model = listResult.Where(m => m.id == item.id).FirstOrDefault();
                    if (pId == 0 && model != null)
                        continue;
                    else
                        listResult.Add(item);
                    ++count;
                    if (listSource.Where(m => m.folder_parent_id == item.id).Count() > 0)
                    {
                        if (!levelNum.Contains(item.id) && addFlag)
                        {
                            addFlag = false;
                            levelNum.Add(item.id);
                        }
                        RefactorFolderLevelList(listSource, item.id, count, levelNum, listResult);
                    }
                    else
                    {
                        if (i < len_tmp_list)
                            continue;
                        levelNum = new List<int>();
                        RefactorFolderLevelList(listSource, 0, count, levelNum, listResult);
                    }
                }
            }
        }
        /// <summary>
        /// 字符串填充
        /// </summary>
        /// <param name="n">填充的次数</param>
        /// <param name="str">需要填充的字符串</param>
        /// <returns></returns>
        private string FillString(int n, string str)
        {
            StringBuilder ret = new StringBuilder();
            for (int i = 0; i < n; i++)
            {
                ret.Append(str);
            }
            return ret.ToString();
        }

效果图：