C#中文件操作主要可以使用StreamReader和StreamWriter两个类

         string infname = "CopyFileAddLineNumber.cs";
         string outfname = "CopyFileAddLineNumber.txt";
         if( args.Length >= 1 ) infname = args[0];
         if( args.Length >= 2 ) outfname = args[1];
   
         try 
         {
             FileStream fin = new FileStream( 
                 infname, FileMode.Open, FileAccess.Read );
             FileStream fout = new FileStream(
                 outfname, FileMode.Create, FileAccess.Write );
   
             StreamReader brin = new StreamReader( 
                 fin, System.Text.Encoding.Default );
             StreamWriter brout  = new StreamWriter(
                 fout, System.Text.Encoding.Default );
   
             int cnt = 0; // 行号
             string s = brin.ReadLine();
             while ( s != null ) 
             {
                 cnt ++; 
                 s = deleteComments(s);                        //去掉以//开始的注释
                 brout.WriteLine(cnt + ": \t" + s );           //写出
                 Console.WriteLine(cnt + ": \t" + s );     //在控制上显示
                 s = brin.ReadLine();                      //读入
             }           
             brin.Close();               // 关闭缓冲读入流及文件读入流的连接.
             brout.Close();
         } 
         catch (FileNotFoundException) 
         {
             Console.WriteLine("File not found!" );
         } 
         catch (IOException e2) 
         {
             Console.WriteLine( e2 );
         }