static void Main(string[] args)
        {
            string Tem_str = "";
             string str = "abcdefg"; //对str字符串逆序输出
            foreach (object i in Transpose(str))
            {
                Tem_str += i.ToString();

            }           
           Console.WriteLine(Tem_str);
          
            Console.ReadKey();
        }

     
       public static IEnumerable<object> Transpose(string n)
        {
           
                for (int i = n.Length - 1; i >= 0; i++)
                {
                    yield return (object)n[i];
                }
          
        }