MatchCollection mat = Regex.Matches("I am a man", @"\w+\b");
            List<string> mclist = new List<string>();
            foreach (Match ma in mat)
            {
                mclist.Add(ma.Value);
            }
            mclist.Reverse();
            foreach (string sm in mclist)
            {
                Console.Write(sm + " ");
            }
           /*
             man a am I
           */

------解决方案--------------------
是不用split吧