This is an EventBus which refered the ApplicationContext.publish(message), which is used to publish an Event in Java Spring.

Normally, EventHandler should be coupled with the Event directly, which is not a good pratice for multi-solution application. This lib provides another different use-case of the Event-Listener parttern: you can separate your EventHandler and Event into different solution or project, and the EventBus can dispatch the event to the corresponding EventHandlers.

What is a correspocorresponding EventHandler?

Suppose you have an event named BaseEvent, There is no doubt an EventHandler like the following code can be invoked by the EventBus

public class BaseHandler: IEventListener<BaseEvent>

Further for, if you have another Event which is an extend of BaseEvent, take the following code as an example:

public class FooEvent: BaseEvent

It is not only a FooEvent, but also a BaseEvent, so the EventListener above can handle it as well.

This is the characteristic of this library

You can install it via nuget

• .NetFramework
• .NetCore

• Reface.EventBus is working based on .NetFramework
• Reface.Core.EventBus is working based on .NetCore

Reface.EventBus

• Nothing

Reface.Core.EventBus

• Microsoft.Extensions.DependencyInjection

Define a New Event

/// <summary>
/// This Event will be publish after the console started
/// </summary>
public class ConsoleStarted : Reface.EventBus.Event
{
    public ConsoleStarted(object source) : base(source)
    {
        Console.WriteLine("Console Started");
    }
}

Publish Event

class Program
{
    static void Main(string[] args)
    {
        // Create an instance of EventBus
        IEventBus eventBus = new DefaultEventBus();

        // Publish the message
        eventBus.Publish(new ConsoleStarted());
    }
}

And class who implements the interface IEventListener<TEvent> would be an event listener.

using ConsoleApp1.Events;
using Reface.EventBus;

namespace ConsoleApp1.Listeners
{
    public class OnConsoleStarted : IEventListener<ConsoleStarted>
    {
        public void Handle(ConsoleStarted @event)
        {
            Console.WriteLine("Console Started");
        }
    }
}

In order to decouple the code, You can register the Listener in the config file

Register listener in web.config / app.config

1. add section
2. add listener

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="eventBus" type="Reface.EventBus.Configuration.EventBusSection, Reface.EventBus"/>
  </configSections>
  <eventBus>
    <listeners>
      <add type="ConsoleApp1.Listeners.OnConsoleStarted, ConsoleApp1" />
    </listeners>
  </eventBus>
</configuration>

除了通过 config 文件的方法，我们还提供了其它方法来注册监听者。

只要实现了 Reface.EventBus.IEventListenerFinder 并在构造 DefaultEventBus 时作为参数传入，便可以订制的方式注册监听者。 目前自带的注册方式有：

• Reface.EventBus.EventListenerFinders.ConfigurationEventListenerFinder 通过 config 文件来注册
• Reface.EventBus.EventListenerFinders.AssembliesEventListenerFinder 通过注册程序集，并返反射其中的类型来得到所有实现了 Reface.EventBus.IEventListenerFinder 的成员
• Reface.EventBus.EventListenerFinders.DefaultEventListenerFinder 通过编码的方式注册监听者

向 IEventListener 的实现类再添加 IPrioritized 接口，并实现 Priority 属性，便可以指定执行的顺序。

• Priority 的值越小，越先执行
• 未实现 IPrioritized 的 IEventListener 认为 Priority = 0

与 IOC/DI 组件的集成，可以免去对监听者一一注册的过程。 在 .NetCore 中，通过为 ServiceCollection 注册必要组件和按程序集注册监听器，可以实现这些功能：

var provider = new ServiceCollection()
  .AddEventBus() // 添加 EventBus 功能
  .AddEventListeners(this.GetType().Assembly)
  .AddEventListeners(typeof(IService).Assembly)
  .BuildServiceProvider();
IEventBus eventBus = provider.GetService<IEventBus>();
eventBus.Publish(new TestEvent());