C# 委托(delegate)和事件？

Question

我有一个带有类的程序集，该类使用委托(delegate)和自定义事件参数定义自定义事件。现在我必须通过我的代码动态加载这个程序集并创建这个类的实例。直到这里我都很好。现在我必须使用自定义委托(delegate)为类对象引发的事件提供事件处理程序。如何使用反射向类引发的事件添加事件处理程序？

Answer 1

代码如下:

 class Program
  {
    static void Main(string[] args)
    {
      // Create publisher.
      var pub = Activator.CreateInstance(typeof(Publisher));
      // Get the event.
      var addEvent = typeof(Publisher).GetEvent("Event");

      // Create subscriber.
      var sub = Activator.CreateInstance(typeof(Subscriber));
      // Get the method.
      var handler = typeof(Subscriber).GetMethod("Handle");
      // Create a valid delegate for it.
      var handlerDelegate = MakeEventHandlerDelegate(handler, sub);

      // Add the event.
      addEvent.AddEventHandler(pub, handlerDelegate);

      // Call the raise method.
      var raise = typeof(Publisher).GetMethod("Raise");
      raise.Invoke(pub, new object[] { "Test Value" });
      Console.ReadLine();
    }

    static Delegate MakeEventHandlerDelegate(MethodInfo methodInfo, object target)
    {
      ParameterInfo[] info = methodInfo.GetParameters();
      if (info.Length != 2)
        throw new ArgumentOutOfRangeException("methodInfo");
      if (!typeof(EventArgs).IsAssignableFrom(info[1].ParameterType))
        throw new ArgumentOutOfRangeException("methodInfo");
      if (info[0].ParameterType != typeof(object))
        throw new ArgumentOutOfRangeException("methodInfo");

      return Delegate.CreateDelegate(typeof(EventHandler<>).MakeGenericType(info[1].ParameterType), target, methodInfo);
    }
  }

  class Args : EventArgs
  {
    public string Value { get; set; }
  }

  class Publisher
  {
    public event EventHandler<Args> Event;

    public void Raise(string value)
    {
      if (Event != null)
      {
        Args a = new Args { Value = value };
        Event(this, a);
      }
    }
  }

  class Subscriber
  {
    public void Handle(object sender, Args args)
    {
      Console.WriteLine("Handle called with {0}.", args.Value);
    }
  }