asp.net 获取指定文件夹下所有子目录及文件(树形)

        {
            DirectoryInfo[] subDirectories = theDir.GetDirectories();//获得目录

            foreach (DirectoryInfo dirinfo in subDirectories)
            {

                Rn += "<option value="" + dirinfo.Name.ToString() + """;
                if (tplPath.ToLower() == dirinfo.Name.ToString().ToLower())
                {
                    Rn += " selected ";
                }
                Rn += ">";

                if (nLevel == 0)
                {
                    Rn += "┣";
                }
                else
                {
                    string _s = "";
                    for (int i = 1; i <= nLevel; i++)
                    {
                        _s += "│ ";
                    }
                    Rn += _s + "┣";
                }
                Rn += "" + dirinfo.Name.ToString() + "</option>";