Is SerialPort in .NET unmanaged resource? Is my wrapped class correct?

Question

I have adapter pattern (wrapper) over serial port class. Should I implement IDisposable pattern and call _wrappedSerialPort.Dispose() in it? There is my class, is it correct?

public class SerialPortAdapter : ISerialPortAdapter
{
    private bool _disposed;

    public event SerialDataReceivedEventHandler DataReceived;

    private readonly SerialPort _wrappedSerialPort;

    public SerialPort WrappedSerialPort
    {
        get { return _wrappedSerialPort; }
    }

    public string PortName
    {
        get { return _wrappedSerialPort.PortName; }
        set { _wrappedSerialPort.PortName = value; }
    }

    public BaudRate BaudRate
    {
        get { return (BaudRate)Enum.ToObject(typeof(BaudRate), _wrappedSerialPort.BaudRate); }
        set { _wrappedSerialPort.BaudRate = (int)value; }
    }

    public bool IsOpen
    {
        get { return WrappedSerialPort.IsOpen; }
    }

    public SerialPortAdapter(SerialPort serialPort)
    {
        _wrappedSerialPort = serialPort;
        _wrappedSerialPort.DataReceived += SerialPortDataReceived;
    }

    public void OpenPort()
    {
        if (!_disposed)
        {
            if (!WrappedSerialPort.IsOpen)
            {

                WrappedSerialPort.Open();

            }
        }
    }


    public void ClosePort()
    {
        if (!_disposed)
        {
            if (WrappedSerialPort.IsOpen)
            {

                WrappedSerialPort.Close();

            }
        }
    }


    public void WriteLine(string request)
    {
    ...
    }


    public void Write(byte[] request)
    {
       ....
    }


    public byte[] Read()
    {
      ....
    }


    public string ReadLine()
    {
       ...
    }


    private void SerialPortDataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        if (DataReceived != null)
        {
            DataReceived(this, e);
        }
    }

    #region IDisposable Members

    public virtual void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    private void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            if (disposing)
            {
                // Dispose managed resources.

            }
            // Dispose unmanaged resources.

            ClosePort();
            WrappedSerialPort.DataReceived -= SerialPortDataReceived;
            _wrappedSerialPort.Dispose();

            _disposed = true;

        }
    }

    ~SerialPortAdapter()
    {

        Dispose(false);
    }

    #endregion
}

Edit: Is it necessary to call this, or is enough to call only _wrappedSerialPort.Dispose();?

        ClosePort();
        WrappedSerialPort.DataReceived -= SerialPortDataReceived;
        _wrappedSerialPort.Dispose();

Answer 1

Henk Holterman's answer is correct: SerialPort is a managed resource, which itself owns an unmanaged resource and hence implements IDisposable.

Since your wrapper owns a SerialPort, it indirectly owns SerialPort's unmanaged resource and hence must implement IDisposable. Your implementation is wrong, the owned SerialPort instance should only be disposed if disposing is true, since it is a managed resource.

It should be implemented as follows:

   private void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            if (disposing)
            {
                // Dispose managed resources.
                ClosePort();
                WrappedSerialPort.DataReceived -= SerialPortDataReceived;
                _wrappedSerialPort.Dispose();
            }
            _disposed = true;
        }
    }

Also, as Henk Holterman points out, you only need a destructor if you directly own unmanaged resources, which is not the case here, and you can simplify the IDisposable implementation by getting rid of the destructor.