.net core 2.0 event bus 一個簡單的基於記憶體事件匯流排實現

1.先定義一個事件介面

public  interface  IEvent
    {
     
    }

2.定義一個事件處理介面

 public  interface  IEventHandler : IEvent
    {
       Task Handle(IEvent e);
    }

3.定義一個發佈介面

public interface IEventPublisher
    {
        Task Publish<TEvent>(TEvent e) where TEvent : IEvent;
    }

4.定義一個訂閱介面

public interface IEventSubscriber 
    {
        
        Task Subscribe<TEvent, EH>() where TEvent : IEvent where EH : class, IEventHandler, new();
    }

5.創建一個類用來存事件

 public static class MemoryMq
    {
        public static ConcurrentDictionary<string, IEvent> eventQueueDict { get; set; }

    }

6.實現發佈類

 public class InMemoryEventPublisher : IEventPublisher
    {
        public Task Publish<TEvent>(TEvent @event) where TEvent : IEvent
        {
            if (@event == null) return Task.CompletedTask;
            if (MemoryMq.eventQueueDict == null)
            {
                MemoryMq.eventQueueDict = new ConcurrentDictionary<string, IEvent>();
            }
            MemoryMq.eventQueueDict.GetOrAdd(Guid.NewGuid().ToString(),@event);
            return Task.CompletedTask;
        }
    }

7.實現訂閱類

public class InMemoryEventSubscriber: IEventSubscriber
    {
        private readonly ConcurrentDictionary<string, Task> taskDict = new ConcurrentDictionary<string, Task>();

   

        public Task Subscribe<TEvent, EH>() where TEvent : IEvent
           where EH : class, IEventHandler, new()
        {
            
            EH state = new EH();
           

            
            Task.Run(() =>
            {
                while (true)
                {
                    if (MemoryMq.eventQueueDict != null)
                    {
                        foreach (var a in MemoryMq.eventQueueDict)
                        {
                            state.Handle(a.Value as IEvent);
                            IEvent o;
                            MemoryMq.eventQueueDict.TryRemove(a.Key ,out o);
                        }
                    }

                }
                
            });
           
            return Task.CompletedTask;
        }
    }

9.測試用例

namespace MemoryMqTest
{
    public class EventHandler : IEventHandler
    {
        public Task Handle(IEvent e, MessagingHelper h)
        {
            switch (e)
            {

                case Order value: Console.WriteLine(value.name); break;
              
            }
            return Task.CompletedTask;

        }

    }
    public class Order : IEvent
    {
        public string name { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {
            var servicecollection = new ServiceCollection();
            servicecollection.AddSingleton<IEventPublisher, InMemoryEventPublisher>();
            servicecollection.AddSingleton<IEventSubscriber, InMemoryEventSubscriber>();
            var provider = servicecollection.BuildServiceProvider();

           var eventPub = provider.GetService<IEventPublisher>();

            var _eventSub = provider.GetService<IEventSubscriber>();

            _eventSub.Subscribe<Order, EventHandler>();


            var order = new Order();
            order.name = "test";
            eventPub.Publish(order);

            Console.WriteLine("Hello World!");

            Console.ReadKey();
        }
    }
}

10.測試結果