RS232串口用事件接受数据（一问一答）

private void button1_Click(object sender, EventArgs e)
{
      serialPort1.Open();
      serialPort1.DataReceived += new   SerialDataReceivedEventHandler(sp5_DataReceived);
      serialPort1.Write(cmdByte, 0, 8);
}
 void sp5_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
      Thread.Sleep(500);
      System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = false;
      SerialPort port = (SerialPort)sender;
      byte[] buf = new byte[50];
      int len = port.Read(buf, 0, buf.Length);
      MessageBox.Show(len.ToString());
      serialPort1.DataReceived -= new SerialDataReceivedEventHandler(sp5_DataReceived);
      port.Close();

  }