在C＃中提出一个事件 [英] Raise an event in C#

问题描述

在Microsoft实践测试中我遇到了这个问题，我感到困惑。这是一个问题：

I came across this question in a Microsoft Practice Test and I got confused. Here is the question:

以下哪个C＃代码示例
是提升事件的正确方法，
假设Alarm事件，
AlarmEventArgs类和
AlarmEventHandler代理已经被声明为
？

Which of the following C# code samples is the proper way to raise an event, assuming that the Alarm event, the AlarmEventArgs class, and the AlarmEventHandler delegate have been declared?

这是他们提供的正确答案：

Here is the "correct" answer they provided:

AlarmEventArgs e = new AlarmEventArgs(1, 2);
AlarmEventHandler handler = Alarm; 
if (handler != null) 
{ 
    handler(this, e);
}

然而，还有一个似乎正确的答案。

However, there is also another answer which seems correct.

AlarmEventArgs e = new AlarmEventArgs(1, 2);
if (Alarm!= null) 
{ 
    Alarm (this, e);
}

我个人总是使用第二种方法。它的工作很好。有人可以告诉我为什么要使用第一种方法而不是第二种方法？

I personally, always use the second method. It works just fine. Can someone please tell me why I should use the first method instead of second?

推荐答案

我问了一个类似的问题。接受的答案是一个很好的解释。

I asked a similar question. The accepted answer is a good explanation.

在事件调度之前检查null ...线程安全？

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