为什么事件在.NET没有返回类型？ [英] Why events have no return types in .NET?

问题描述

事件还'不'类似方法，但他们没有返回类型，只是空洞？

Events also 'does' something like methods, but they don't have return types and just voids?

我很想知道，为什么会这样呢？而他们为什么不返回值的类型？

I am curious to know, Why is it so? and Why don't they return types?

推荐答案

由于事件可以由多个监听器来处理。还有就是不能保证为事件处理程序（虽然我认为他们在他们订阅在现实中的顺序是所谓的。）

Because events can be handled by multiple listeners. There is not guaranteed order to the event handlers (though I think they're called in the order they are subscribed in reality.)

相反，对于那些希望回归的一些数据事件，该公约是有一个可变EventArgs对象，如CancelEventArgs它可以有它的取消属性设置为true。这在一个返回值的优点是链的事件处理程序可以看看属性，看看其他处理程序已经设置。但你还是风的情况是，最后一个设置属性的胜利。

Instead, for events that want to "return" some data, the convention is to have a mutable EventArgs object such as CancelEventArgs which can have its Cancel property set to true. The advantage of this over a return value is that event handlers in the chain can look at the property to see if another handler already set it. But you still wind up with a situation where the last one to set the property wins.

如果它是一个返回值，整个概念将是一个复杂多了。

If it were a return value, the whole concept would be a lot more complicated.

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