visual studio 2013 -如何使用c#访问COM-Port

这里串行通信端口显示错误，无法访问.....但是串行通信端口在arduino中工作完美，所以它不能是端口问题，它也不是驱动程序问题，驱动程序更新并且工作良好，所以问题可以在代码.....中我是c#的新手。

public partial class Form1 : Form
{
    private SerialPort myport;
    private string in_data;
    public Form1()
    {
        InitializeComponent();
    }
    private void Start_Click(object sender, EventArgs e)
    {
        myport = new SerialPort();
        myport.BaudRate = 19200;
        myport.PortName = pn.Text;
        myport.Parity = Parity.None;
        myport.DataBits = 8;
        myport.StopBits = StopBits.One;
        myport.DataReceived += myport_DataReceived;
        try
        {
            myport.Open();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Error!!");
        }
    }
    void myport_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        *in_data = myport.ReadLine();***
        this.Invoke(new EventHandler(displaydata_event));
    }
    private void displaydata_event(object sender, EventArgs e)
    {
        string[] newData = in_data.Split(',');
        bv.Text = newData[0];
        bi.Text = newData[1];
        pv.Text = newData[2];
        pi.Text = newData[3];
        t.Text = newData[4];
    }
}