string strOld = "aaaaaa\r\nbbbbbb\r\ncccccc\r\ndddddd\r\neeeeee\r\nffffff\r\n";
            string[] strTemp = strOld.Split("\r\n".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
            ArrayList alNew = new ArrayList();
            Random r = new Random();
            while (true)
            {
                int i = r.Next(0, strTemp.Length);
                if (!alNew.Contains(strTemp[i]))
                    alNew.Add(strTemp[i]);
                if (alNew.Count == strTemp.Length)
                    break;
            }

            foreach (object obj in alNew)
            {
                Console.WriteLine(obj);
            }