C#弱事件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;

namespace WeakCarInfoEventManager
{
    //弱事件是为了回收清空侦听器所拥对象内存
    class Program
    {
        static void Main(string[] args)
        {
            var dealer = new CarDealer();

            var michael = new Consumer("Michael");
            WeakCarInfoEventManager.AddListener(dealer, michael);

            dealer.NewCar("Mercedes");

            var nick = new Consumer("Nick");
            WeakCarInfoEventManager.AddListener(dealer, nick);

            dealer.NewCar("Ferrari");

            WeakCarInfoEventManager.RemoveListener(dealer, michael);

            dealer.NewCar("Toyota");
        }
    }
    public class WeakCarInfoEventManager : WeakEventManager
    {
        public static void AddListener(object source, IWeakEventListener listener)
        {
            CurrentManager.ProtectedAddListener(source, listener);

        }
        public static void RemoveListener(object source, IWeakEventListener listener)
        {
            CurrentManager.ProtectedRemoveListener(source, listener);
        }
        public static WeakCarInfoEventManager CurrentManager
        {
            get
            {
                WeakCarInfoEventManager manager = GetCurrentManager(typeof(WeakCarInfoEventManager)) as WeakCarInfoEventManager;
                if (manager == null)
                {
                    manager = new WeakCarInfoEventManager();
                    SetCurrentManager(typeof(WeakCarInfoEventManager), manager);
                }
                return manager;
            }
        }
        protected override void StartListening(object source)
        {
            (source as CarDealer).NewCarInfo += CarDealer_NewCarInfo;
        }
        protected override void StopListening(object source)
        {
            (source as CarDealer).NewCarInfo -= CarDealer_NewCarInfo;
        }
        void CarDealer_NewCarInfo(object sender, CarInfoEventArgs e)
        {
            DeliverEvent(sender, e);
        }
    }

    public class Consumer : IWeakEventListener
    {
        private string name;
        public Consumer(string name)
        {
            this.name = name;
        }
        public void NewCarIsHere(object sender, CarInfoEventArgs e)
        {
            Console.WriteLine("{0}:car{1} is new ",name,e.Car);
        }
        bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
        {
            NewCarIsHere(sender, e as CarInfoEventArgs);
            return true;
        }
 
    }
}

 

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

namespace WeakCarInfoEventManager
{
    public class CarInfoEventArgs : EventArgs
    {
        public CarInfoEventArgs(string car)
        {
            this.Car = car;
        }

        public string Car { get; private set; }
    }
    public class CarDealer
    {
        public event EventHandler<CarInfoEventArgs> NewCarInfo;

        public CarDealer()
        {

        }

        public void NewCar(string car)
        {
            Console.WriteLine("CarDealer, new car {0}", car);
            if (NewCarInfo != null)
            {
                NewCarInfo(this, new CarInfoEventArgs(car));
            }
        }
    }
}