相关疑难解决方法(0)

术语"CPU绑定"和"I/O绑定"是什么意思？

使用Parallel.ForEach或Task.Run()以异步方式启动一组任务有什么区别？

版本1:

List<string> strings = new List<string> { "s1", "s2", "s3" };
Parallel.ForEach(strings, s =>
{
    DoSomething(s);
});

版本2:

List<string> strings = new List<string> { "s1", "s2", "s3" };
List<Task> Tasks = new List<Task>();
foreach (var s in strings)
{
    Tasks.Add(Task.Run(() => DoSomething(s)));
}
await Task.WhenAll(Tasks);

// let's say there is a list of 1000+ URLs
string[] urls = { "http://google.com", "http://yahoo.com", ... };

// now let's send HTTP requests to each of these URLs in parallel
urls.AsParallel().ForAll(async (url) => {
    var client = new HttpClient();
    var html = await client.GetStringAsync(url);
});

这是问题所在,它会同时启动1000多个Web请求.有没有一种简单的方法来限制这些异步http请求的并发数量？这样在任何给定时间都不会下载超过20个网页.如何以最有效的方式做到这一点？