使闭包捕获的变量易变

问题描述：

闭包捕获的变量如何与不同的线程交互？在下面的示例代码中，我想将totalEvents声明为volatile，但是C＃不允许这样做。

How do variables captured by a closure interact with different threads? In the following example code I would want to declare totalEvents as volatile, but C# does not allow this.

（是的，我知道这是不好的代码，这只是一个示例）

(Yes I know this is bad code, it's just an example)

private void WaitFor10Events()
{
     volatile int totalEvents = 0; // error CS0106:

     _someEventGenerator.SomeEvent += (s, e) => totalEvents++;

     while(totalEvents < 10)
        Thread.Sleep(100);
}

编辑：人们似乎没有抓住重点我的问题。我知道我不能在本地变量上使用 volatile 。我也知道示例代码是错误的，可以用其他方式实现，因此我的错误代码免责声明。

EDIT: People seem to be missing the point of my question a bit. I know I can't use volatile on local vars. I also know that the example code code is bad and could be implemented in other ways, hence my "bad code" disclaimer. It was just to illustrate the problem.

无论如何，似乎没有办法将易失性语义强加到捕获的局部变量上，所以我将采用另一种方式。不过，感谢您的回答，我还是学到了一些有用的东西。：）

Anyway, it would appear that there is no way to force volatile semantics onto captured local variables, so I will implement a different way. Thanks for the answers though, I have learned a couple of useful things anyway. :)

答

Volatile。编写救援文件：

Volatile.Write to the rescue:

private void WaitFor10Events()
{
     int totalEvents = 0; 

     _someEventGenerator.SomeEvent += (s, e) => Volatile.Write(ref totalEvents, totalEvents+1);

     while(totalEvents < 10)
        Thread.Sleep(100);
}

也就是说，我仍然会使用 Interlocked.Increment 针对这种情况。

That said, I would still use Interlocked.Incrementfor this particular case..

使闭包捕获的变量易变

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