FileStream file= new FileStream(fileName,FileMode.Open,FileAccess.ReadWrite);
   
   StreamReader sr = new StreamReader(file,Encoding.Default);
   
   
    for(int i=0;i<file.Length;i++)
    {
     //char c=br.ReadChar();
     char c=Convert.ToChar(file.ReadByte());
     switch(c)
     {
      case '\n':
       Console.Write(@"\n");
       Console.Write("\n");

       break;
      case '\r':
       Console.Write(@"\r");
       Console.Write("\r");

       break;
      case ' ':
       Console.Write("_");

       break;
      default:
       Console.Write(c);
  
       break;
     }
    }
   Console.Read();

   sr.Close();

注：不能用binaryReader，读取大文件跳出缓冲区溢出，未找到解决办法；
        此function读取中文出错。