C#  读COM PORT

参照了MSDN的示例：

https://msdn.microsoft.com/en-us/library/system.io.ports.serialport.aspx

还是不工作，需要加这一行代码：

mySerialPort.DtrEnable = true;

DtrEnable属性的描述：

Gets or sets a value that enables the Data Terminal Ready (DTR) signal during serial communication.

demo代码：

public class COMPortListener
    {
        private static ILog logger = LogManager.GetLogger(typeof (COMPortListener));

        #region single instance
        private COMPortListener()
        {
        }
        static COMPortListener()
        {

        }
        private static COMPortListener _instance = new COMPortListener();
        public static COMPortListener Instance { get { return _instance; } }

        #endregion

        public Action<string> OnDataReceived;

        public void SerialPortListenAsync()
        {
            if (OnDataReceived == null)
            {
                throw new InvalidOperationException("must set callback [OnDataReceived] first.");
            }

            Task.Run(() =>
            {
                var mySerialPort = new SerialPort(ConfigurationManager.AppSettings["COM_PORT"]);

                mySerialPort.BaudRate = 9600;
                mySerialPort.Parity = Parity.None;
                mySerialPort.StopBits = StopBits.One;
                mySerialPort.DataBits = 8;
                mySerialPort.Handshake = Handshake.None;
                mySerialPort.RtsEnable = true;
                mySerialPort.DtrEnable = true;

                mySerialPort.ReadTimeout = 500;

                mySerialPort.ErrorReceived += (sender, args) =>
                {
                    Console.WriteLine("######error");
                    Console.WriteLine(args.EventType);
                };
                mySerialPort.Open();
                logger.Info("####COM PORT opened...");
                while (true)
                {
                    try
                    {
                        string message = mySerialPort.ReadLine();
                        OnDataReceived(message);
                        Task.Delay(500);
                    }
                    catch (TimeoutException ex)
                    {
                        //do nothing
                    }
                }

            });

        }
    }