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)
            {

                if (nLevel == 0)
                {
                    Rn += "├";
                }
                else
                {
                    string _s = "";
                    for (int i = 1; i <= nLevel; i++)
                    {
                        _s += "│ ";
                    }
                    Rn += _s + "├";
                }
                Rn += "<b>" + dirinfo.Name.ToString() + "</b><br />";
                FileInfo[] fileInfo = dirinfo.GetFiles();   //目录下的文件
                foreach (FileInfo fInfo in fileInfo)
                {
                    if (nLevel == 0)
                    {