C#文件写下操作

using System;using System.IO;namespace IO操作{    class Program    {        static void Main(string[] args)        {            using(StreamWriter w=File.AppendText("IO.txt"))            {                TextIn("Hello GeoStorm", w);                TextIn("Hello World",w);                w.Close();            }        }        public static void TextIn(string content, TextWriter w)        {            w.Write("\r\n message:");            w.WriteLine("{0}",content);            w.Flush();        }    }}