运行多个异步任务并等待它们全部完成

我需要在控制台应用程序中运行多个异步任务，并在进一步处理之前等待它们全部完成。

有很多文章，但我似乎越读越困惑。我已经阅读并理解了Task库的基本原理，但我显然在某个地方遗漏了一个链接。

我知道可以将任务串联起来，这样它们就可以在另一个任务完成后开始(这几乎是我读过的所有文章的场景)，但我希望所有任务同时运行，并且我想知道它们都完成后的情况。

对于这样的场景，最简单的实现是什么?

当前回答

如果你正在使用async/await模式，你可以像这样并行运行几个任务:

public async Task DoSeveralThings()
{
    // Start all the tasks
    Task first = DoFirstThingAsync();
    Task second = DoSecondThingAsync();

    // Then wait for them to complete
    var firstResult = await first;
    var secondResult = await second;
}

2021-08-03 11:41:48

其他回答

这是我如何使用数组Func<>:

var tasks = new Func<Task>[]
{
   () => myAsyncWork1(),
   () => myAsyncWork2(),
   () => myAsyncWork3()
};

await Task.WhenAll(tasks.Select(task => task()).ToArray()); //Async    
Task.WaitAll(tasks.Select(task => task()).ToArray()); //Or use WaitAll for Sync

2017-05-23 11:30:08

还有另一个答案……但我通常会遇到这样的情况，当我需要同时加载数据并将其放入变量中，比如:

var cats = new List<Cat>();
var dog = new Dog();

var loadDataTasks = new Task[]
{
    Task.Run(async () => cats = await LoadCatsAsync()),
    Task.Run(async () => dog = await LoadDogAsync())
};

try
{
    await Task.WhenAll(loadDataTasks);
}
catch (Exception ex)
{
    // handle exception
}

2018-10-17 11:53:04

你可以使用WhenAll，它将返回一个可等待的任务，或者WaitAll，它没有返回类型，将阻止进一步的代码执行，类似于线程。休眠，直到所有任务都完成、取消或出错。

	`WhenAll`	`WaitAll`
Any of the supplied tasks completes in a faulted state	A task with the faulted state will be returned. The exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.	An `AggregateException` will be thrown.
None of the supplied tasks faulted but at least one of them was canceled	The returned task will end in the `TaskStatus.Canceled` state	An `AggregateException` will be thrown which contains an `OperationCanceledException` in its `InnerExceptions` collection
An empty list was given	An `ArgumentException` will be thrown	The returned task will immediately transition to a `TaskStatus.RanToCompletion` State before it's returned to the caller.
	Doesn't block the current thread	Blocks the current thread

例子

var tasks = new Task[] {
    TaskOperationOne(),
    TaskOperationTwo()
};

Task.WaitAll(tasks);
// or
await Task.WhenAll(tasks);

如果你想以特定的顺序运行任务，你可以从这个答案中得到灵感。

2017-06-16 21:21:26

你可以创建很多任务，比如:

List<Task> TaskList = new List<Task>();
foreach(...)
{
   var LastTask = new Task(SomeFunction);
   LastTask.Start();
   TaskList.Add(LastTask);
}

Task.WaitAll(TaskList.ToArray());

2014-07-29 06:45:42

如果你正在使用async/await模式，你可以像这样并行运行几个任务:

public async Task DoSeveralThings()
{
    // Start all the tasks
    Task first = DoFirstThingAsync();
    Task second = DoSecondThingAsync();

    // Then wait for them to complete
    var firstResult = await first;
    var secondResult = await second;
}

2021-08-03 11:41:48

运行多个异步任务并等待它们全部完成

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