操作文件系统（2）二进制文件的建、写、读

private void Button3_Click(object sender, System.EventArgs e)
  {
   //写二进制文件
   BinaryWriter bw;
      //创建一个二进制文件
   FileStream fs=new FileStream (MapPath("mydata.data"),FileMode.Create );
   bw=new BinaryWriter (fs);//初始化一个BinaryWriter
   for(int i=0;i<200;i++)
    bw.Write (i);//写入
   bw.Close ();//关闭
  }

  private void Button4_Click(object sender, System.EventArgs e)
  {
   //读二进制文件
   BinaryReader br;
   string str="";
   FileStream fs=new FileStream (MapPath("mydata.data"),FileMode.Open );
   br=new BinaryReader (fs);  
   for(int i=0;i<fs.Length /4;i++)
     str+=br.ReadInt32 ().ToString ();
   TextBox1.Text =str;
  }