在 ASP.NET MVC 控制器中处理域事件

Question

我正在考虑使用 域事件 来冒泡信息发生在我的域模型深处的操作，以便在控制器级别发出某些事件的信号。不幸的是，我无法找到如何在 ASP.NET MVC 控制器上正确连接它的示例。

简而言之，这就是我在行动中寻找的东西：

service.doSomethingComplicated();
var model = new ViewModel();
model.somethingComplicatedCausedSomethingElse = <true-if-my-domain-event-was-raised>;
return View(model);

任何人都可以为我提供一些指导吗？

更新

需要明确的是，我了解如何在控制器中引发和处理域事件；我只是在寻找一种注册事件的实现，该实现可以在我描述的上下文中安全使用。

Answer 1

根据您链接到的示例，作者在其中执行此操作：

Customer preferred = null;

DomainEvents.Register<CustomerBecamePreferred>(
    p => preferred = p.Customer
        );

c.DoSomething();

您应该能够执行以下操作：

    var model = new ViewModel();

    // Register a handler that sets your bool to true if / when the event is raised
    DomainEvents.Register<YourDomainEvent>(e => model.somethingComplicatedCausedSomethingElse = true);
    // EDIT: If using the singleUseActions modification, pass the second parameter
    // DomainEvents.Register<YourDomainEvent>(e => model.somethingComplicatedCausedSomethingElse = true, true);

    // Call the service. If it raises the event, the handler you just registered will set your bool
    service.doSomethingComplicated();

    return View(model);

编辑（DomainEvents 修改）
这是未经测试并在 StackOverflow 编辑框中编写的，但这是我开始的地方。我使用一个可选参数，以便不需要修改现有的调用，并使用一个单独的列表“singleUseActions”来尽可能保持现有的内容不变。希望有帮助。

public static class DomainEvents
  { 
      [ThreadStatic] //so that each thread has its own callbacks
      private static List<Delegate> actions;

      [ThreadStatic] //so that each thread has its own callbacks
      private static List<Delegate> singleUseActions;

      public static IContainer Container { get; set; } //as before

      //Registers a callback for the given domain event
      public static void Register<T>(Action<T> callback, bool isSingleUse = false) where T : IDomainEvent
      {
         List<Delegate> targetList;
         if (isSingleUse)
         {
             if (singleUseActions == null) singleUseActions = new List<Delegate>();
             targetList = singleUseActions;
         }
         else
         {
             if (actions == null) actions = new List<Delegate>();
             targetList = actions;
         }

         targetList.Add(callback);
     }

     //Clears callbacks passed to Register on the current thread
     public static void ClearCallbacks ()
     {
         actions = null;
         singleUseActions = null;
     }

     //Raises the given domain event
     public static void Raise<T>(T args) where T : IDomainEvent
     {
        if (Container != null)
           foreach(var handler in Container.ResolveAll<Handles<T>>())
              handler.Handle(args);

        if (actions != null)
            foreach (var action in actions)
                if (action is Action<T>)
                    ((Action<T>)action)(args);

        if (singleUseActions != null)
            // Don't foreach because we are going to modify the collection
            for (int index = singleUseActions.Count - 1; index > -1; index--)
            {
                var singleUseAction = singleUseActions[index];
                if (singleUseAction is Action<T>)
                {
                    ((Action<T>)singleUseAction)(args);
                    singleUseActions.RemoveAt(index);
                }
            }


  }
}