C＃点网络核心从网络框架dll扩展类

Question

I have one class library project built on dot net framework 3.5. I want to have a new dot net core application reference the dll produced by the first project and extend classes from that library.

I have had to add a nuget reference to Microsoft.NETCore.Portable.Compatibility to make fix some basic issues with doing this, but now when I extend a class with an abstract method I can't override the method. I get a paradoxical situation where the class is raising an error that the method is not implemented and the method is raising an error that there is nothing to override.

Is there some way to work around this or is it not supported by dot net core at all?

base class (dot net framework 3.5 class library):

public abstract class Server {
    public event Action<Connection> ConnectionEstablished;

    private TcpListener m_listenSocket;
    private Task m_awaitConnectionTask;
    readonly private List<Action> m_serverStoppedCallbacks = new List<Action>();

    protected Server(int port) {
        m_listenSocket = new TcpListener(IPAddress.Parse("localhost"), port);
    }

    public void Listen() {
        m_listenSocket.Start();
        m_awaitConnectionTask = new Task(AwaitConnection);
    }

    public void WhenStopped(Action callback) {
        lock(m_serverStoppedCallbacks)
            m_serverStoppedCallbacks.Add(callback);
    }

    protected abstract Connection CreateConnection(TcpClient tcpClient);

    private void AwaitConnection() {
        try {
            while (true) 
                ConnectionEstablished?.Invoke(CreateConnection(m_listenSocket.AcceptTcpClient()));
        } catch (SocketException e) {

        } finally {
            m_listenSocket.Stop();
            List<Action> callbacks;
            lock (m_serverStoppedCallbacks) {
                callbacks = m_serverStoppedCallbacks.ToList();
                m_serverStoppedCallbacks.Clear();
            }
            foreach (var callback in callbacks)
                callback();
        }
    }
}

inheriting class (dot net core command line application):

public class Server : Communism.Network.Server {
    public Server(int port) : base(port) {
    }

    public static void Main() {

    }

    protected override Connection CreateConnection(TcpClient tcpClient) {
        return null;
    }
}

After more investigation the problem is being caused by the TcpClient type. If I make the signature of CreateConnection take no parameters or build in types I can extend fine. It might be because the Compatibility package resolves the TcpClient class as different from the TcpClient class which the library was compiled against. I don't know enough about how the Compatibility package works to figure out a solution for this.

Here is a complete repository with all the projects set up so that you get the same error. Just open the solution in visual studio 2017. https://github.com/strigonLeader/dotnetcoreexample

Answer 1

The only time I've seen something like this happen is when VS is using an old version of a binary. I've been burned by it before because I forgot to clean the solution, or when VS has some kind of issue finding a reference and automatically resolves to a copy it found in the ninth layer of hell. You might also want to see if you are targeting the same framework if the two classes are in different projects.