asp.net 获取指定文件夹下所有子目录及文件(树形)

                FileInfo[] fileInfo = dirinfo.GetFiles();   //目录下的文件
                foreach (FileInfo fInfo in fileInfo)
                {
                    Rn += "<option value="" + dirinfo.Name.ToString()+"/"+fInfo.Name.ToString() + """;
                    if (tplPath.ToLower() == fInfo.Name.ToString().ToLower())
                    {
                        Rn += " selected ";
                    }
                    Rn += ">";

                    if (nLevel == 0)
                    {
                        Rn += "│ ├";
                    }
                    else
                    {
                        string _f = "";
                        for (int i = 1; i <= nLevel; i++)
                        {
                            _f += "│ ";