在C＃中多路广播委托使用组播 [英] Use of multicast in C# multicast delegates

问题描述

当它是有用的具有多路广播委托过singlecast代表？

我用的代表很多，主要是加上C＃lambda表达式，但我从来没有觉得使用C＃的代表组播方面，即我从来没有想多与会代表结合在一起在一个委托的冲动。因此，我很好奇在什么样的情况下多路广播委托的是有用的 - 我只能想到的例子中，你可以很容易地实现该功能是以其他方式，比方说，链代表，或将它们放在一个列表

在特定的，埃里克利珀的回答<一href="http://stackoverflow.com/questions/2306814/co-and-contravariance-bugs-in-net-4-0/2307942#2307942">here给人的IM pression甚至C＃团队有时会忘掉代表的multicastiness。

解决方案

任何作为一个事件是经典的答案在这里 - 那么调用者并不需要知道谁是听（只是调用它，如果它是非空值）。这是一个理想的多个操作可以同时订阅 - 例如3个独立的控制观察（数据绑定）到一个视图模型相同的属性。

在任何情况下，委托充当功能（特别是与一个返回值）是特里克，因为你需要考虑你将如何处理的 - 拿第一？持续？总结？

When is it useful to have multicast delegates over singlecast delegates?

I use delegates a lot, mainly coupled with C# lambdas, but I've never felt the urge to use the multicast aspect of C# delegates, ie I've never wanted to combine multiple delegates together in a single delegate. I'm therefore very curious in what sort of situation multicast delegates are useful - I can only think of examples in which you can easily implement the functionality some other way, by, say, chaining the delegates or putting them in a list.

In particular, Eric Lippert's answer here gives the impression even the C# team sometimes forgets about the multicastiness of delegates.

解决方案

Anything acting as an event is the classic answer here - then the caller doesn't need to know who is listening (just invoke it, if it is non-null). This is ideal as multiple operations can subscribe simultaneously - for example 3 separate controls observing (data-binding) to the same property on a view-model.

Any cases where the delegate is acting as function (in particular with a return value) is tricker, as you need to think how you will handle that - take the first? Last? Aggregate?

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