字符串管理

        static void Main(string[] args)
        {
            StringBuilder sb = new StringBuilder();
            TextWriter tw = new StringWriter(sb);
            tw.WriteLine("Hello!");
            tw.WriteLine("现在的时间是{0}。", DateTime.Now);
            tw.WriteLine("Bye!");

            TextReader tr = new StringReader(sb.ToString());
            Console.WriteLine(tr.ReadToEnd());
        }