using (StreamReader sr = new StreamReader(@"C:\Documents and Settings\Administrator\桌面\1.txt",Encoding.Default)) 
        //    {
        //        string a=sr.ReadLine();
        //        Console.Write(a);
        //    }
            using (StreamWriter sr = new StreamWriter(@"C:\Documents and Settings\Administrator\桌面\1.txt",true,Encoding.Default))
            {
                string s="我是个一个神";
               
                sr.Write(s);
                
            }
            Console.ReadKey();
原文:http://www.cnblogs.com/mengluo/p/4932552.html