.net FileStream加密

FileStream fsread = new FileStream(textBox1.Text, FileMode.Open, FileAccess.Read);
FileStream fswrite = new FileStream(textBox2.Text, FileMode.Create, FileAccess.Write);
byte[] bytes = new byte[1024 * 3];
int r = 0;
while ((r = fsread.Read(bytes, 0, bytes.Length)) > 0)
      {
      //加密其实就是先把byte[]中的字节内容先改变一下，再写入操作
      //fswrite.Write(bytes, 0, r);
      for (int i = 0; i < r; i++)
      {
          bytes[i] = (byte)(byte.MaxValue - bytes[i]);
      }
      fswrite.Write(bytes, 0, r);
}
fswrite.Dispose();
fsread.Dispose();
MessageBox.Show("OK");