Task.WhenAll中是否有任务完成时的回调 [英] Is there a callback for when a task is completed in Task.WhenAll

问题描述

假设我有以下内容:

IEnumerable<Task<TimeSpan>> tasks = //...
TimeSpan[] results = await Task.WhenAll(tasks);
// Handle results

等到我可以处理所有任务必须完成的结果时.

By the time I can handle the results all the task must have finished.

是否有一种方法可以按需处理每个结果??

Is there a way to handle each result on demand?

就像注册一个将在任务完成时执行的委托/回调一样:

Like registering a delegate / callback that will get executed when a task is completed:

IEnumerable<Task<TimeSpan>> tasks = //...
await Task.WhenAll(tasks, result =>
{
   // A task has finished. This will get executed.
   // result is of type TimeSpan
});

推荐答案

有没有一种方法可以按需处理每个结果?

Is there a way to handle each result on demand?

是的，您使用WhenAny而不是WhenAll ...或在每个任务上调用ContinueWith.

Yes, you use WhenAny instead of WhenAll... or call ContinueWith on each task.

例如，对于WhenAny方法:

ISet<Task<TimeSpan>> tasks = new HashSet<Task<TimeSpan>>(...);
while (tasks.Count != 0)
{
    var task = await Task.WhenAny(tasks);
    // Use task here
    tasks.Remove(task);
}

您可以使用另一个选项，将原始任务序列转换为按顺序完成但给出相同结果的任务序列.详细信息在此博客帖子，但结果是您可以使用:

There's another option you could use, where you transform the original sequence of tasks into a sequence of tasks which completes in order, but giving the same results. Details are in this blog post, but the result is that you can use:

foreach (var task in tasks.InCompletionOrder())
{
    var result = await task;
    // Use the result
}

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