Wpf 服务器/客户端登录。 事件问题

Question

I'm pretty new to programming, so bear with me if my question isn't specific enough. Right now I'm trying to make a simple Client Logon to my server. So the server App knows which users are connected. When a client connects I want an event to fire on the server that update the userlist. But it doesn't and I can't figure out why. Hope you can help.

In the codes I have removed how the users should be displayed in the serverApp. Right now I just need the event to work.

In my Service Library:

INetworkService contract:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace NetworkLib
{
    [ServiceContract]
    public interface INetworkService
    {
        [OperationContract]
        void Logon(UserInfo userInfo);

        [OperationContract]
        void Logout();
    }
}

NetworkService Class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace NetworkLib
{
    public class NetworkService : INetworkService
    {
        public event EventHandler UserListChanged;

        public void Logon(UserInfo userInfo)
        {
            OnUserListChanged();
        }

        public void Logout()
        {
            OnUserListChanged();
        }

        private void OnUserListChanged()
        {
            var handler = UserListChanged;
            if (handler != null)
            {
                handler(this, EventArgs.Empty);
            }
        }
    }
}

UserInfo Class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Serialization;

namespace NetworkLib
{
    [DataContract]
    public class UserInfo
    {
        [DataMember]
        public string Name;
    }
}

In my ServerApp (WPF):

using System.ServiceModel;
using NetworkLib;

namespace ServerApp
{
    public partial class MainWindow : Window
    {

        NetworkService networkService;

        public MainWindow()
        {
            InitializeComponent();

            ServiceHost host = new ServiceHost(typeof(NetworkService));

            host.Open();

            networkService = new NetworkService();

            networkService.UserListChanged += networkService_UserListChanged;

        }

        private void networkService_UserListChanged(object sender, EventArgs e)
        {
            MessageBox.Show("It Works!");
        }
    }
}

In my ClientApp (WPF): (Have made a Service Reference to the Server)

namespace ClientApp
{

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            ServiceReference.NetworkServiceClient proxy = new ServiceReference.NetworkServiceClient();

            ServiceReference.UserInfo userInfo = new ServiceReference.UserInfo();

            userInfo.Name = "Test";

            proxy.Logon(userInfo);

        }
    }
}

Answer 1

You subscribe to event of other NetworkService instance than ServiceHost instantiates. In your case every time you make request to server, new NetworkService instance is created. Place the following attribute above NetworkService class:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]

Then subscribe to event:

var serviceInstance = (NetworkService)host.SingletonInstance;
serviceInstance.UserListChanged += networkService_UserListChanged;

Answer 2

When creating your ServiceHost, you should provide NetworkService instance instead of typeof(NetworkService)

ServiceHost host = new ServiceHost(networkService);

You need to initialize it first, of course.

Answer 3

I didnt look in great detail but overall your code looks ok. It is sometimes useful in this situation to run 2 instances of VisualStudio - one for server in debug and one for client in debug. If you put a break point in client button1_Click code in VS thats debugging client, and a break point in NetworkServices.Logout in VS thats debugging server you will be able to step from client to server code and see easily whats going wrong where.

Answer 4

Why do you need an event model here? Why not just handle your "event" directly in NetworkService.Logout(). Does pushing this off to an event and then having to wire that event (which as ilya.dofofeev correctly points out is not on the same object) provide any real benefit?