你可以使用Task。如前所述，WhenAll或Task。WaitAll，这取决于您是否希望线程等待。看看这两个解释的链接。

WaitAll vs WhenAll

如果您试图记录所有错误，请确保您保留任务。代码中的WhenAll行，很多注释建议您可以删除它并等待单个任务。的任务。WhenAll对于错误处理非常重要。如果没有这一行，您可能会为未观察到的异常打开代码。

var catTask = FeedCat();
var houseTask = SellHouse();
var carTask = BuyCar();

await Task.WhenAll(catTask, houseTask, carTask);

var cat = await catTask;
var house = await houseTask;
var car = await carTask;

假设FeedCat在以下代码中抛出异常:

var catTask = FeedCat();
var houseTask = SellHouse();
var carTask = BuyCar();

var cat = await catTask;
var house = await houseTask;
var car = await carTask;

在这种情况下，您将永远不会等待houseTask或carTask。这里有3种可能的场景:

SellHouse is already completed successfully when FeedCat failed. In this case you are fine. SellHouse is not complete and fails with exception at some point. Exception is not observed and will be rethrown on finalizer thread. SellHouse is not complete and contains awaits inside it. In case your code runs in ASP.NET SellHouse will fail as soon as some of the awaits will completed inside it. This happens because you basically made fire & forget call and synchronization context was lost as soon as FeedCat failed.

下面是你将得到的case(3)的错误:

System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Web.ThreadContext.AssociateWithCurrentThread(Boolean setImpersonationContext)
   at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext)
   at System.Web.HttpApplication.System.Web.Util.ISyncContext.Enter()
   at System.Web.Util.SynchronizationHelper.SafeWrapCallback(Action action)
   at System.Threading.Tasks.Task.Execute()
   --- End of inner exception stack trace ---
---> (Inner Exception #0) System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Web.ThreadContext.AssociateWithCurrentThread(Boolean setImpersonationContext)
   at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext)
   at System.Web.HttpApplication.System.Web.Util.ISyncContext.Enter()
   at System.Web.Util.SynchronizationHelper.SafeWrapCallback(Action action)
   at System.Threading.Tasks.Task.Execute()<---

对于情况(2)，您将得到类似的错误，但原始异常堆栈跟踪。

对于. net 4.0及更高版本，您可以使用TaskScheduler.UnobservedTaskException捕获未观察到的异常。对于。net 4.5及以后的版本，未观察到的异常将被默认接受，而对于。net 4.0，未观察到的异常将使您的进程崩溃。

更多详细信息请参见。net 4.5中的任务异常处理

var dn = await Task.WhenAll<dynamic>(FeedCat(),SellHouse(),BuyCar());

如果你想访问Cat，你可以这样做:

var ct = (Cat)dn[0];

这是非常简单的做法和非常有用的使用，没有必要去追求一个复杂的解决方案。

当你使用WhenAll后，你可以用await单独拉出结果:

var catTask = FeedCat();
var houseTask = SellHouse();
var carTask = BuyCar();

await Task.WhenAll(catTask, houseTask, carTask);

var cat = await catTask;
var house = await houseTask;
var car = await carTask;

[注意异步方法总是返回“热”(已经启动的)任务。]

你也可以使用Task。结果(因为此时您知道它们都已成功完成)。但是，我推荐使用await，因为它显然是正确的，而Result在其他场景中可能会导致问题。

只需要分别等待这三个任务，在启动它们之后:

var catTask = FeedCat();
var houseTask = SellHouse();
var carTask = BuyCar();

var cat = await catTask;
var house = await houseTask;
var car = await carTask;

注意:如果任何一个任务抛出异常，这段代码可能会在后面的任务完成之前返回异常，但它们都将运行。在几乎所有的情况下，当你已经知道结果是理想的时候就不要等待。在边缘情况下，可能不是这样。

The three tasks in your example differ greatly in importance. In case one of them fails, you probably want to know what happened with the others. For example in case the communication with the automatic cat feeder failed, you don't want to miss whether selling your house succeeded or failed. So it makes sense to return back not just a Cat, a House and a Tesla, but the tasks themselves. The calling code will then be able to query separately each of the three tasks, and react appropriately to their successful or failed completions:

public async Task<(Task<Cat>, Task<House>, Task<Tesla>)> FeedCatSellHouseBuyCar()
{
    Task<Cat> task1 = FeedCat();
    Task<House> task2 = SellHouse();
    Task<Tesla> task3 = BuyCar();

    // All three tasks are launched at this point.

    try { await Task.WhenAll(task1, task2, task3).ConfigureAwait(false); } catch { }

    // All three tasks are completed at this point.
    
    return (task1, task2, task3);
}

使用的例子:

var (catTask, houseTask, teslaTask) = await FeedCatSellHouseBuyCar();

// All three tasks are completed at this point.

if (catTask.IsCompletedSuccessfully)
    Console.WriteLine($"{catTask.Result.Name} is eating her healthy meal.");
else
    Console.WriteLine("Your cat is starving!");

if (houseTask.IsCompletedSuccessfully)
    Console.WriteLine($"Your house at {houseTask.Result.Address} was sold. You are now rich and homeless!");
else
    Console.WriteLine("You are still the poor owner of your house.");

if (teslaTask.IsCompletedSuccessfully)
    Console.WriteLine($"You are now the owner a battery-powered {teslaTask.Result.Name}.");
else
    Console.WriteLine("You are still driving a Hyundai.");

带有空catch的try块是必需的，因为. net 7仍然没有提供适当的方法来等待任务，而不会在取消或失败时抛出。