SerialPortIo

public interface ISerialPortIo : IDisposable
{
    string PortName { get; }
    string ReadLine();
    void WriteLine(string text);
}

public class SerialPortConfig
{
    public string Name { get; private set; }
    public int BaudRate { get; private set; }
    public int DataBits { get; private set; }
    public StopBits StopBits { get; private set; }
    public Parity Parity { get; private set; }
    public bool DtrEnable { get; private set; }
    public bool RtsEnable { get; private set; }

    public SerialPortConfig(
        string name,
        int baudRate,
        int dataBits,
        StopBits stopBits,
        Parity parity,
        bool dtrEnable,
        bool rtsEnable)
    {
        if (String.IsNullOrWhiteSpace(name)) throw new ArgumentNullException("name");

        this.RtsEnable = rtsEnable;
        this.BaudRate = baudRate;
        this.DataBits = dataBits;
        this.StopBits = stopBits;
        this.Parity = parity;
        this.DtrEnable = dtrEnable;
        this.Name = name;
    }

    public override string ToString()
    {
        return String.Format(
            "{0} (Baud: {1}/DataBits: {2}/Parity: {3}/StopBits: {4}/{5})",
            this.Name,
            this.BaudRate,
            this.DataBits,
            this.Parity,
            this.StopBits,
            this.RtsEnable ? "RTS" : "No RTS");
    }
}

// Wrapper around SerialPort
public class SerialPortIo : ISerialPortIo
{
    protected ILog Log { get; private set; }
    static readonly ILog s_Log = LogManager.GetLogger(typeof(SerialPortIo));

    readonly SerialPort _port;
    readonly Stream _internalSerialStream;

    public SerialPortIo(SerialPortConfig portConfig)
    {
        if (portConfig == null) throw new ArgumentNullException("portConfig");

        this.Log = LogManager.GetLogger(this.GetType());

        // http://zachsaw.blogspot.com/2010/07/net-serialport-woes.html
        SerialPortFixer.Execute(portConfig.Name);

        var port = new SerialPort(
            portConfig.Name,
            portConfig.BaudRate,
            portConfig.Parity,
            portConfig.DataBits,
            portConfig.StopBits)
        {
            RtsEnable = portConfig.RtsEnable,
            DtrEnable = portConfig.DtrEnable,
            ReadTimeout = 5000,
            WriteTimeout = 5000
        };
        port.Open();

        try
        {
            this._internalSerialStream = port.BaseStream;
            this._port = port;
            this._port.DiscardInBuffer();
            this._port.DiscardOutBuffer();
        }
        catch (Exception ex)
        {
            Stream internalStream = this._internalSerialStream;

            if (internalStream == null)
            {
                FieldInfo field = typeof(SerialPort).GetField(
                    "internalSerialStream",
                    BindingFlags.Instance | BindingFlags.NonPublic);

                // This will happen if the SerialPort class is changed
                // in future versions of the .NET Framework
                if (field == null)
                {
                    this.Log.WarnFormat(
                        "An exception occured while creating the serial port adaptor, "
                        + "the internal stream reference was not acquired and we were unable "
                        + "to get it using reflection. The serial port may not be accessible "
                        + "any further until the serial port object finalizer has been run: {0}",
                        ex);

                    throw;
                }

                internalStream = (Stream)field.GetValue(port);
            }

            this.Log.DebugFormat(
                "An error occurred while constructing the serial port adaptor: {0}", ex);

            SafeDisconnect(port, internalStream);
            throw;
        }
    }

    public string PortName
    {
        get { return this._port.PortName; }
    }

    public string ReadLine()
    {
        return this._port.ReadTo(Environment.NewLine);
    }

    public void WriteLine(string text)
    {
        this._port.Write(text);
        this._port.Write("\r");
    }

    public void Dispose()
    {
        this.Dispose(true);
    }

    protected void Dispose(bool disposing)
    {
        SafeDisconnect(this._port, this._internalSerialStream);

        if (disposing)
        {
            GC.SuppressFinalize(this);
        }
    }

    /// <summary>
    /// Safely closes a serial port and its internal stream even if
    /// a USB serial interface was physically removed from the system
    /// in a reliable manner.
    /// </summary>
    /// <param name="port"></param>
    /// <param name="internalSerialStream"></param>
    /// <remarks>
    /// The <see cref="SerialPort"/> class has 3 different problems in disposal
    /// in case of a USB serial device that is physically removed:
    ///
    /// 1. The eventLoopRunner is asked to stop and <see cref="SerialPort.IsOpen"/>
    /// returns false. Upon disposal this property is checked and closing
    /// the internal serial stream is skipped, thus keeping the original
    /// handle open indefinitely (until the finalizer runs which leads to the next problem)
    ///
    /// The solution for this one is to manually close the internal serial stream.
    /// We can get its reference by <see cref="SerialPort.BaseStream" />
    /// before the exception has happened or by reflection and getting the
    /// "internalSerialStream" field.
    ///
    /// 2. Closing the internal serial stream throws an exception and closes
    /// the internal handle without waiting for its eventLoopRunner thread to finish,
    /// causing an uncatchable ObjectDisposedException from it later on when the finalizer
    /// runs (which oddly avoids throwing the exception but still fails to wait for
    /// the eventLoopRunner).
    ///
    /// The solution is to manually ask the event loop runner thread to shutdown
    /// (via reflection) and waiting for it before closing the internal serial stream.
    ///
    /// 3. Since Dispose throws exceptions, the finalizer is not suppressed.
    ///
    /// The solution is to suppress their finalizers at the beginning.
    /// </remarks>
    static void SafeDisconnect(SerialPort port, Stream internalSerialStream)
    {
        GC.SuppressFinalize(port);
        GC.SuppressFinalize(internalSerialStream);

        ShutdownEventLoopHandler(internalSerialStream);

        try
        {
            s_Log.DebugFormat("Disposing internal serial stream");
            internalSerialStream.Close();
        }
        catch (Exception ex)
        {
            s_Log.DebugFormat(
                "Exception in serial stream shutdown of port {0}: {1}", port.PortName, ex);
        }

        try
        {
            s_Log.DebugFormat("Disposing serial port");
            port.Close();
        }
        catch (Exception ex)
        {
            s_Log.DebugFormat("Exception in port {0} shutdown: {1}", port.PortName, ex);
        }
    }

    static void ShutdownEventLoopHandler(Stream internalSerialStream)
    {
        try
        {
            s_Log.DebugFormat("Working around .NET SerialPort class Dispose bug");

            FieldInfo eventRunnerField = internalSerialStream.GetType()
                .GetField("eventRunner", BindingFlags.NonPublic | BindingFlags.Instance);

            if (eventRunnerField == null)
            {
                s_Log.WarnFormat(
                    "Unable to find EventLoopRunner field. "
                    + "SerialPort workaround failure. Application may crash after "
                    + "disposing SerialPort unless .NET 1.1 unhandled exception "
                    + "policy is enabled from the application's config file.");
            }
            else
            {
                object eventRunner = eventRunnerField.GetValue(internalSerialStream);
                Type eventRunnerType = eventRunner.GetType();

                FieldInfo endEventLoopFieldInfo = eventRunnerType.GetField(
                    "endEventLoop", BindingFlags.Instance | BindingFlags.NonPublic);

                FieldInfo eventLoopEndedSignalFieldInfo = eventRunnerType.GetField(
                    "eventLoopEndedSignal", BindingFlags.Instance | BindingFlags.NonPublic);

                FieldInfo waitCommEventWaitHandleFieldInfo = eventRunnerType.GetField(
                    "waitCommEventWaitHandle", BindingFlags.Instance | BindingFlags.NonPublic);

                if (endEventLoopFieldInfo == null
                    || eventLoopEndedSignalFieldInfo == null
                    || waitCommEventWaitHandleFieldInfo == null)
                {
                    s_Log.WarnFormat(
                        "Unable to find the EventLoopRunner internal wait handle or loop signal fields. "
                        + "SerialPort workaround failure. Application may crash after "
                        + "disposing SerialPort unless .NET 1.1 unhandled exception "
                        + "policy is enabled from the application's config file.");
                }
                else
                {
                    s_Log.DebugFormat(
                        "Waiting for the SerialPort internal EventLoopRunner thread to finish...");

                    var eventLoopEndedWaitHandle =
                        (WaitHandle)eventLoopEndedSignalFieldInfo.GetValue(eventRunner);
                    var waitCommEventWaitHandle =
                        (ManualResetEvent)waitCommEventWaitHandleFieldInfo.GetValue(eventRunner);

                    endEventLoopFieldInfo.SetValue(eventRunner, true);

                    // Sometimes the event loop handler resets the wait handle
                    // before exiting the loop and hangs (in case of USB disconnect)
                    // In case it takes too long, brute-force it out of its wait by
                    // setting the handle again.
                    do
                    {
                        waitCommEventWaitHandle.Set();
                    } while (!eventLoopEndedWaitHandle.WaitOne(2000));

                    s_Log.DebugFormat("Wait completed. Now it is safe to continue disposal.");
                }
            }
        }
        catch (Exception ex)
        {
            s_Log.ErrorFormat(
                "SerialPort workaround failure. Application may crash after "
                + "disposing SerialPort unless .NET 1.1 unhandled exception "
                + "policy is enabled from the application's config file: {0}",
                ex);
        }
    }
}