如何限制 Parallel.ForEach? [英] How can I limit Parallel.ForEach?

问题描述

我有一个 Parallel.ForEach() 异步循环，我用它下载了一些网页.我的带宽有限，所以我每次只能下载 x 页，但 Parallel.ForEach 会执行所需网页的整个列表.

I have a Parallel.ForEach() async loop with which I download some webpages. My bandwidth is limited so I can download only x pages per time but Parallel.ForEach executes whole list of desired webpages.

有没有办法在运行 Parallel.ForEach 时限制线程数或任何其他限制器?

Is there a way to limit thread number or any other limiter while running Parallel.ForEach?

演示代码:

Parallel.ForEach(listOfWebpages, webpage => {
  Download(webpage);
});

真正的任务与网页无关，因此创造性的网络抓取解决方案无济于事.

The real task has nothing to do with webpages, so creative web crawling solutions won't help.

推荐答案

您可以在 ParallelOptions 参数中指定 MaxDegreeOfParallelism:

You can specify a MaxDegreeOfParallelism in a ParallelOptions parameter:

Parallel.ForEach(
    listOfWebpages,
    new ParallelOptions { MaxDegreeOfParallelism = 4 },
    webpage => { Download(webpage); }
);

MSDN:Parallel.ForEach

MSDN:ParallelOptions.MaxDegreeOfParallelism

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