private void btnWrite_Click(object sender, EventArgs e)
{
    SerialPort serialPort = new SerialPort();
    serialPort.PortName = "COM1";//串口名稱
    serialPort.BaudRate = 9600; //獲取或設(shè)置波特率
    serialPort.Parity = Parity.Even;//獲取或設(shè)置校驗(yàn)位
    serialPort.DataBits = 8;//獲取或設(shè)置數(shù)據(jù)位默認(rèn)值8
    serialPort.StopBits = StopBits.One;// 停止位
    serialPort.Open();
    serialPort.Write("A");
    serialPort.Close();
}

SerialPort serialPort = new SerialPort();
private void btnRead_Click(object sender, EventArgs e)
{


    byte[] a = System.Text.Encoding.ASCII.GetBytes(" ");
    serialPort.PortName = "COM1";//串口名稱
    serialPort.BaudRate = 9600; //獲取或設(shè)置波特率
    serialPort.Parity = Parity.None;//獲取或設(shè)置校驗(yàn)位
    serialPort.DataBits = 8;//獲取或設(shè)置數(shù)據(jù)位默認(rèn)值8
    serialPort.StopBits = StopBits.One;// 停止位
    serialPort.DataReceived += SerialPort_DataReceived;
    serialPort.Open();
}


private void SerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    byte[] b = new byte[8];
    int A = serialPort.Read(b, 0, 8);
    this.Invoke(() =>
    {
        string s = ByteToHex(b);
        txtValue.Text += s+System.Environment.NewLine;
    });
}


public string ByteToHex(byte[] Bytes)
{
    string str = string.Empty;
    foreach (byte Byte in Bytes)
    {
        str += String.Format("{0:X2}", Byte) + " ";
    }
    return str.Trim();
}

using System.IO.Ports;


namespace SCOM
{
    public partial class FrmMain : Form
    {
        SerialPort serialPort;
        public FrmMain()
        {
            InitializeComponent();
            Init();
        }


        private void LoadPorts()
        {
            cboPort.Items.Clear();
            string[] port = System.IO.Ports.SerialPort.GetPortNames();
            foreach (var item in port)
            {
                cboPort.Items.Add(item);
            }
            cboPort.SelectedIndex = 0;
        }


        private void Init()
        {
            LoadPorts();
            object[] baudRate = { 4800, 9600, 19200, 38400, 57600, 115200, 230400 };
            cboBaudRate.Items.AddRange(baudRate);
            cboBaudRate.SelectedIndex = 1;


            cboDataBits.Items.Add(7);
            cboDataBits.Items.Add(8);
            cboDataBits.SelectedIndex = 1;


            cboStopBits.Items.Add("One");
            cboStopBits.Items.Add("OnePointFive");
            cboStopBits.Items.Add("Two");
            cboStopBits.SelectedIndex = 0;


            //Parity
            cboParity.Items.Add("None");
            cboParity.Items.Add("Even");
            cboParity.Items.Add("Mark");
            cboParity.Items.Add("Odd");
            cboParity.Items.Add("Space");
            cboParity.SelectedIndex = 0;


            cboHandshaking.Items.Add("None");
            cboHandshaking.Items.Add("XOnXOff");
            cboHandshaking.Items.Add("RequestToSend");
            cboHandshaking.Items.Add("RequestToSendXOnXOff");
            cboHandshaking.SelectedIndex = 0;
            btnClosePort.Enabled = false;
        }


        private void btnRefresh_Click(object sender, EventArgs e)
        {
            LoadPorts();
        }


        private void btnOpenPort_Click(object sender, EventArgs e)
        {
            if (serialPort == null)
            {
                serialPort = new SerialPort();
            }
            serialPort.PortName = cboPort.Text;//串口名稱
            serialPort.BaudRate = int.Parse(cboBaudRate.Text); //獲取或設(shè)置波特率
            serialPort.Parity = (Parity)Enum.Parse(typeof(Parity), cboParity.Text);//獲取或設(shè)置校驗(yàn)位
            serialPort.DataBits = int.Parse(cboDataBits.Text);//獲取或設(shè)置數(shù)據(jù)位默認(rèn)值8
            serialPort.StopBits = (StopBits)Enum.Parse(typeof(StopBits), cboStopBits.Text);// 停止位
            serialPort.Handshake = (Handshake)Enum.Parse(typeof(Handshake), cboHandshaking.Text);// 握手協(xié)議
            serialPort.DataReceived += SerialPort_DataReceived;
            serialPort.Open();
            stsMain_lblStatus.Text = "端口已打開(kāi)";
            btnOpenPort.Enabled = false;
            btnClosePort.Enabled = true;
        }


        private void SerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            this.Invoke(new Action(() =>
            {
                byte[] b = new byte[8];
                int A = serialPort.Read(b, 0, 8);
                string s = "";
                if (rdoHex.Checked)
                {
                    s = ByteToHex(b);
                }
                else
                {
                    s = System.Text.Encoding.Default.GetString(b);
                }
                txtReceive.AppendText(System.Environment.NewLine+ s);
            }));
        }


        private void btnClosePort_Click(object sender, EventArgs e)
        {
            if (serialPort != null && serialPort.IsOpen)
            {
                serialPort.DataReceived -= SerialPort_DataReceived;
                serialPort.Close();
                stsMain_lblStatus.Text = "端口已關(guān)閉";
                btnOpenPort.Enabled = true;
                btnClosePort.Enabled = false;
            }
        }


        private void btnSend_Click(object sender, EventArgs e)
        {
            if (serialPort == null || !serialPort.IsOpen)
            {
                return;
            }
            serialPort.Write(txtSend.Text);
        }


        private string ByteToHex(byte[] Bytes)
        {
            string str = string.Empty;
            foreach (byte Byte in Bytes)
            {
                str += String.Format("{0:X2}", Byte) + " ";
            }
            return str.Trim();
        }
    }
}