请说明Timer事件异步/等待语法 [英] Please explain Timer event async/await syntax

问题描述

我研究了异步并等待语法此处和here 。它真的有助于了解使用情况，但我发现一个有趣的语法示例在 MSDN ，我只是不明白。

I researched the asynch and await syntax here and here. It really helps to understand the usage but I found an intriguing syntax example on MSDN which I just don't understand.

问题：
可以有人请向我解释这个 System.Timers.Timer 事件注册与asynch等待的语法：
为什么可以使用 async await 已经在lambda表达式中的关键字

Question: Could someone please explain to me the syntax of this System.Timers.Timer event registration with asynch await: Why can you use the async await keywords already in the lambda expression?

Timer timer = new Timer(1000);
timer.Elapsed += async ( sender, e ) => await HandleTimer();

private Task HandleTimer()
{
    Console.WriteLine("\nHandler not implemented..." );        
}

问题2：
什么是两个参数发件人& e 如果它们没有出现在 HandleTimer 方法中，那么很好？

Question 2: And what are the two parameters sender & e good for if they don't appear in the HandleTimer method?

推荐答案

它为$ code> timer Elapsed 事件分配一个async lambda C>。你可以这样理解async lambda：首先，以下是lambda：

It assigns an async lambda to the Elapsed event of timer. You can understand the async lambda this way: first, the following is a lambda:

(sender, e) => HandleTimer()

此lambda同时调用 HandleTimer 。然后我们添加一个等待以异步方式调用 HandleTimer

this lambda calls HandleTimer synchronously. Then we add an await to call HandleTimer asynchronously:

(sender, e) => await HandleTimer()

但这不会工作，因为要异步调用异步你必须是异步的，因此 async 关键字：

but this won't work because to call something asynchronously you have to be asynchronous yourself, hence the async keyword:

async (sender, e) => await HandleTimer()

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