C＃闭包，为什么是loopvariable参照抓获？ [英] C# Closures, why is the loopvariable captured by reference?

问题描述

在这个例子中，我试图按值传递，但引用，而不是通过。

In this example, I'm attempting to pass by value, but the reference is passed instead.

for (int i = 0; i < 10; i++)
{
    Thread t = new Thread(() => new PhoneJobTest(i);
    t.Start();
}

这是可以纠正的，像这样：

This can be remedied like so:

 for (int i = 0; i < 10; i++)
{
    int jobNum = i;
    Thread t = new Thread(() => new PhoneJobTest(jobNum);
    t.Start();
}

什么是怎么回事？为什么原来的例子将引用传递？

What's is going on here? Why does the original example pass the reference?

推荐答案

好吧，这是多么的C＃工程。在你的语句中的拉姆达前pression构建了一个封闭的词汇，它存储的单一参考 I 的持续循环已经结束后还是一样。

Well, that's just how C# works. The lambda expression in your statement constructs a lexical closure, which stores a single reference to i that persists even after the loop has concluded.

要解决它，你可以做到这一点，你做的东西。

To remedy it, you can do just the thing that you did.

随意阅读更多关于这个具体问题各地的网络;我的选择是<一个href=\"http://blogs.msdn.com/ericlippert/archive/2009/11/12/closing-over-the-loop-variable-considered-harmful.aspx\">Eric利珀特的讨论在这里。

Feel free to read more on this particular issue all around the Web; my choice would be Eric Lippert's discussion here.

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