确定事件是否已附加到 [英] Determine if an event has been attached to yet

问题描述

我有两个对象 - 一个包含一些代码将会触发一个事件，一个包含该事件的处理程序。因为第二个对象的实例还不存在，所以加载第一个对象中的AddHandler不能。当我提出我的事件时，我想检查一下object2的副本是否被实例化（容易做到），如果一个处理程序已经附加到事件（不知道该怎么做）。

我也可以另外建议如何做到这一点。如果我在Object1.Load中添加了AddHandler，并且Object2还不存在，那么即使稍后创建它也不会处理我的事件。现在，在触发事件的代码中，我刚刚使用了一个RemoveHandler，然后每次发生一个AddHandler，然后我知道当对象终于存在时，我会附加，但是我知道这个是一个糟糕的方法。

我看到一篇关于类似的文章（确定绑定到事件的事件处理程序列表），也许我在翻译中缺少某些东西，但是我无法使代码在我的自定义事件在VB.NET中。

解决方案

你也可以在挂钩事件之前检查一个bool字段。 >

 如果不是eventHooked然后
 addhandler 
 eventHooked = true 
结束如果
  

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I have two objects - one that contains some code with will fire an event, and one that contains the handler for that event. I can't "AddHandler" in the Load of the first object, because an instance of the second object doesn't exist yet. When I raise my event, I want to check to see if a copy of object2 has been instantiated (easy to do), and if a handler has been attached to the event yet (not sure how to do this).

I'm also open to another recommendation about how to do this instead. If I do my AddHandler in Object1.Load, and Object2 doesn't exist yet, then it will never handle my event, even if I create it later. Right now, in the code that fires the event, I've just resorted to doing a RemoveHandler and then an AddHandler every single time the event is raised, and then I know I'll attach when the object finally exists, but I know this is a crappy method.

I saw an article about something similar (Determine list of event handlers bound to event), and maybe I'm missing something in the translation, but I can't get the code to work on my custom event in VB.NET.

解决方案

You could also just have a bool field that you check before hooking the event.

if not eventHooked then
 addhandler
 eventHooked = true
end if

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