Question

我正在尝试实现简单的事件总线

我是这样开始的：

public class RegistrationData
{
    public object RegisteredObject { get; set; }
    public Type eventType { get; set; }
    public EventHandler MethodToInvoke;
}
public class EventBus
{
    private static EventBus instance;
    private static readonly object lockObject = new object();
    private static List<RegistrationData> registrationList;

    private EventBus()
    {
    }

    public static EventBus Instance
    {
        get
        {
            lock (lockObject)
            {
                registrationList = new List<RegistrationData>();
                return instance ?? new EventBus();
            }
        }
    }

    public void Subscribe(RegistrationData registrationData)
    {
        if(!registrationList.Contains(registrationData)) registrationList.Add(registrationData);
    }

    public void Unsubscribe(object objectToUnregister, Type eventType)
    {
        foreach(RegistrationData data in registrationList)
            if (data.RegisteredObject == objectToUnregister && data.eventType == eventType) registrationList.Remove(data);
    }

    public void UnregisterAllMessages(object objectToUnregister)
    {
        foreach(RegistrationData data in registrationList)
            if(data.RegisteredObject == objectToUnregister) registrationList.Remove(data);
    }

    public void PublishEvent(object sender, EventArgs eventArgs)
    {
        foreach (RegistrationData data in registrationList)
            if (EventArgs is typeof(data.Type)) data.MethodToInvoke(sender, eventArgs);
    }
}

但我在PublishEvent方法中遇到问题。我无法确定事件参数的类型。而且我怀疑这一切都是错误的。

有人可以指出我做错了什么，我应该如何实现？或者如何通常实现事件总线，或者我可以使用的一些框架，而不是实现我自己并花费时间。

Answer 1

嗯，不确定您的Eventbus应该如何表现。如果不知道你要去哪里，那么看看其他人如何实现这个问题会很有用。

有一个脚踏实地的event aggregator in the caliburn.micro项目
当我需要一个事件聚合器时，我喜欢使用MemBus，部分原因是我自己写的，部分是因为它涵盖了我在这方面的所有需求。它比caliburn的更多参与，但它具有更多功能

Answer 2

我认为你应该从定义事件总线开始。您认为事件总线与用于触发和下沉事件的内置.NET机制之间的区别是什么？到目前为止，您所拥有的内容似乎只能实现相当于.NET事件的功能。 .NET本质上支持事件处理，因此如果您不需要超过.NET已提供的内容，则不需要事件总线：

class Program
{
  static void Main(string[] args)
  {
     BusinessObject1 bo = new BusinessObject1("First Value");
     // Subscribe
     bo.Publish += new BusinessObject.PublishObject(bo_Publish);
     bo.Update("Second Value");
     // UnSubscribe
     bo.Publish -= new BusinessObject.PublishObject(bo_Publish);
     bo.Update("Third Value");
     // Subscribe multiple
     bo.Publish += new BusinessObject.PublishObject(bo_Publish);
     bo.Publish += new BusinessObject.PublishObject(bo_Publish2);
     bo.Update("Fourth Value");
     // UnregisterAllMessages
     bo.UnsubcribeAll();
     bo.Update("Fifth Value");
  }

  static void bo_Publish(BusinessObject sender, EventArgs args)
  {
     if (sender is BusinessObject1)
     {
        BusinessObject1 bo1 = (BusinessObject1)sender;
        BusinessObject1.PublishBusinessObject1EventArgs args1 =
           (BusinessObject1.PublishBusinessObject1EventArgs)args;
        Console.WriteLine("Updated {0} to {1}", args1.oldValue, bo1.Value);
     }
  }

  static void bo_Publish2(BusinessObject sender, EventArgs args)
  {
     if (sender is BusinessObject1)
     {
        BusinessObject1 bo1 = (BusinessObject1)sender;
        BusinessObject1.PublishBusinessObject1EventArgs args1 =
           (BusinessObject1.PublishBusinessObject1EventArgs)args;
        Console.WriteLine("Second handler detected updated of {0} to {1}", args1.oldValue, bo1.Value);
     }
  }
}

abstract class BusinessObject
{
  public delegate void PublishObject(BusinessObject sender, EventArgs args);
  public event PublishObject Publish;
  // PublishEvent
  protected void Update(EventArgs args)
  {
     if (Publish != null)
        Publish(this, args);
  }
  public void UnsubcribeAll()
  {
     Publish = null;
  }
}

class BusinessObject1 : BusinessObject
{
  public class PublishBusinessObject1EventArgs : EventArgs
  {
     public string oldValue;
     public PublishBusinessObject1EventArgs(string oldValue)
     {
        this.oldValue = oldValue;
     }
  }

  public delegate void PublishBusinessObject1(BusinessObject1 sender, PublishBusinessObject1EventArgs args);

  public string Value {get; private set;}

  public BusinessObject1(string value)
  {
     this.Value = value;
  }

  public void Update(string newValue)
  {
     PublishBusinessObject1EventArgs args = new PublishBusinessObject1EventArgs(Value);
     Value = newValue;
     base.Update(args);
  }
}

修改如果您不希望业务对象必须从公共基类继承（如您在评论中所建议的那样），您可以进行一些修改，以便EventBus更独立，但您仍然不需要重新实现所有的事件注册框架都是这样做的：

class Program { static void Main(string[] args) { BusinessObject1 bo = new BusinessObject1("First Value"); // Subscribe EventBus.Publish += new EventBus.PublishObject(EventBus_Publish); bo.Update("Second Value"); // UnSubscribe EventBus.Publish -= new EventBus.PublishObject(EventBus_Publish); bo.Update("Third Value"); // Subscribe multiple EventBus.Publish += new EventBus.PublishObject(EventBus_Publish); EventBus.Publish += new EventBus.PublishObject(EventBus_Publish2); bo.Update("Fourth Value"); // UnregisterAllMessages EventBus.UnsubcribeAll(); bo.Update("Fifth Value"); } static void EventBus_Publish(object sender, EventArgs args) { if (sender is BusinessObject1) { BusinessObject1 bo1 = (BusinessObject1)sender; BusinessObject1.PublishBusinessObject1EventArgs args1 = (BusinessObject1.PublishBusinessObject1EventArgs)args; Console.WriteLine("Updated {0} to {1}", args1.oldValue, bo1.Value); } } static void EventBus_Publish2(object sender, EventArgs args) { if (sender is BusinessObject1) { BusinessObject1 bo1 = (BusinessObject1)sender; BusinessObject1.PublishBusinessObject1EventArgs args1 = (BusinessObject1.PublishBusinessObject1EventArgs)args; Console.WriteLine("Second handler detected updated of {0} to {1}", args1.oldValue, bo1.Value); } } } static class EventBus { public delegate void PublishObject(object sender, EventArgs args); public static event PublishObject Publish; // PublishEvent public static void Update(object sender, EventArgs args) { if (Publish != null) Publish(sender, args); } public static void UnsubcribeAll() { Publish = null; } } class BusinessObject1 { public class PublishBusinessObject1EventArgs : EventArgs { public string oldValue; public PublishBusinessObject1EventArgs(string oldValue) { this.oldValue = oldValue; } } public delegate void PublishBusinessObject1(BusinessObject1 sender, PublishBusinessObject1EventArgs args); public string Value { get; private set; } public BusinessObject1(string value) { this.Value = value; } public void Update(string newValue) { PublishBusinessObject1EventArgs args = new PublishBusinessObject1EventArgs(Value); Value = newValue; EventBus.Update(this, args); } }

编辑2：顺便说一句，如果您想要更多地控制订阅过程，您可以通过定义自定义事件访问器来获得更多控制权，如http://msdn.microsoft.com/en-us/library/bb882534.aspx所述：

static class EventBus { public delegate void PublishObject(object sender, EventArgs args); private static List<PublishObject> subscribers = new List<PublishObject>(); public static event PublishObject Publish { add { subscribers.Add(value); Console.WriteLine("Added subscriber {0}.{1}", value.Method.DeclaringType.Name, value.Method.Name); } remove { bool result = subscribers.Remove(value); Console.WriteLine("Removed subscriber {0}.{1} ({2})", value.Method.DeclaringType.Name, value.Method.Name, result ? "success" : "failure"); } } // PublishEvent public static void Update(object sender, EventArgs args) { foreach (PublishObject p in subscribers) { Console.WriteLine("Publishing to {0}.{1}", p.Method.DeclaringType.Name, p.Method.Name); p.Invoke(sender, args); } } public static void UnsubcribeAll() { subscribers.Clear(); } }

Answer 3

嗯，作为第一个建议，它看起来好像你试图将它作为一个单身人士来实现。否则，

会是什么

private static EventBus instance;

有益吗？但私有实例成员从未被分配到任何地方，这是我建议您应该修复的一件事。有关单身人士各种实施的here's a really good article供参考。如果您有权访问.net4，我建议您使用LazySingleton3方法。

唯一想到的是，看起来它可能是 Generics 的用例。看看EventHandler<TEventArgs> Delegate。

除此之外，我不能推荐更多，因为我不完全明白你想要做什么。

修改

查看the accepted answer上的this question。它包含指向几年前实现此功能的blog post人的链接。好像你不需要重新发明轮子。

事件总线实施问题

3 个答案: