我很想看看问题中提供的方法和公认答案的结果，所以我对它进行了测试。

代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace AsyncTest
{
    class Program
    {
        class Worker
        {
            public int Id;
            public int SleepTimeout;

            public async Task DoWork(DateTime testStart)
            {
                var workerStart = DateTime.Now;
                Console.WriteLine("Worker {0} started on thread {1}, beginning {2} seconds after test start.",
                    Id, Thread.CurrentThread.ManagedThreadId, (workerStart-testStart).TotalSeconds.ToString("F2"));
                await Task.Run(() => Thread.Sleep(SleepTimeout));
                var workerEnd = DateTime.Now;
                Console.WriteLine("Worker {0} stopped; the worker took {1} seconds, and it finished {2} seconds after the test start.",
                   Id, (workerEnd-workerStart).TotalSeconds.ToString("F2"), (workerEnd-testStart).TotalSeconds.ToString("F2"));
            }
        }

        static void Main(string[] args)
        {
            var workers = new List<Worker>
            {
                new Worker { Id = 1, SleepTimeout = 1000 },
                new Worker { Id = 2, SleepTimeout = 2000 },
                new Worker { Id = 3, SleepTimeout = 3000 },
                new Worker { Id = 4, SleepTimeout = 4000 },
                new Worker { Id = 5, SleepTimeout = 5000 },
            };

            var startTime = DateTime.Now;
            Console.WriteLine("Starting test: Parallel.ForEach...");
            PerformTest_ParallelForEach(workers, startTime);
            var endTime = DateTime.Now;
            Console.WriteLine("Test finished after {0} seconds.\n",
                (endTime - startTime).TotalSeconds.ToString("F2"));

            startTime = DateTime.Now;
            Console.WriteLine("Starting test: Task.WaitAll...");
            PerformTest_TaskWaitAll(workers, startTime);
            endTime = DateTime.Now;
            Console.WriteLine("Test finished after {0} seconds.\n",
                (endTime - startTime).TotalSeconds.ToString("F2"));

            startTime = DateTime.Now;
            Console.WriteLine("Starting test: Task.WhenAll...");
            var task = PerformTest_TaskWhenAll(workers, startTime);
            task.Wait();
            endTime = DateTime.Now;
            Console.WriteLine("Test finished after {0} seconds.\n",
                (endTime - startTime).TotalSeconds.ToString("F2"));

            Console.ReadKey();
        }

        static void PerformTest_ParallelForEach(List<Worker> workers, DateTime testStart)
        {
            Parallel.ForEach(workers, worker => worker.DoWork(testStart).Wait());
        }

        static void PerformTest_TaskWaitAll(List<Worker> workers, DateTime testStart)
        {
            Task.WaitAll(workers.Select(worker => worker.DoWork(testStart)).ToArray());
        }

        static Task PerformTest_TaskWhenAll(List<Worker> workers, DateTime testStart)
        {
            return Task.WhenAll(workers.Select(worker => worker.DoWork(testStart)));
        }
    }
}

结果输出:

Starting test: Parallel.ForEach...
Worker 1 started on thread 1, beginning 0.21 seconds after test start.
Worker 4 started on thread 5, beginning 0.21 seconds after test start.
Worker 2 started on thread 3, beginning 0.21 seconds after test start.
Worker 5 started on thread 6, beginning 0.21 seconds after test start.
Worker 3 started on thread 4, beginning 0.21 seconds after test start.
Worker 1 stopped; the worker took 1.90 seconds, and it finished 2.11 seconds after the test start.
Worker 2 stopped; the worker took 3.89 seconds, and it finished 4.10 seconds after the test start.
Worker 3 stopped; the worker took 5.89 seconds, and it finished 6.10 seconds after the test start.
Worker 4 stopped; the worker took 5.90 seconds, and it finished 6.11 seconds after the test start.
Worker 5 stopped; the worker took 8.89 seconds, and it finished 9.10 seconds after the test start.
Test finished after 9.10 seconds.

Starting test: Task.WaitAll...
Worker 1 started on thread 1, beginning 0.01 seconds after test start.
Worker 2 started on thread 1, beginning 0.01 seconds after test start.
Worker 3 started on thread 1, beginning 0.01 seconds after test start.
Worker 4 started on thread 1, beginning 0.01 seconds after test start.
Worker 5 started on thread 1, beginning 0.01 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.01 seconds after the test start.
Worker 2 stopped; the worker took 2.00 seconds, and it finished 2.01 seconds after the test start.
Worker 3 stopped; the worker took 3.00 seconds, and it finished 3.01 seconds after the test start.
Worker 4 stopped; the worker took 4.00 seconds, and it finished 4.01 seconds after the test start.
Worker 5 stopped; the worker took 5.00 seconds, and it finished 5.01 seconds after the test start.
Test finished after 5.01 seconds.

Starting test: Task.WhenAll...
Worker 1 started on thread 1, beginning 0.00 seconds after test start.
Worker 2 started on thread 1, beginning 0.00 seconds after test start.
Worker 3 started on thread 1, beginning 0.00 seconds after test start.
Worker 4 started on thread 1, beginning 0.00 seconds after test start.
Worker 5 started on thread 1, beginning 0.00 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.00 seconds after the test start.
Worker 2 stopped; the worker took 2.00 seconds, and it finished 2.00 seconds after the test start.
Worker 3 stopped; the worker took 3.00 seconds, and it finished 3.00 seconds after the test start.
Worker 4 stopped; the worker took 4.00 seconds, and it finished 4.00 seconds after the test start.
Worker 5 stopped; the worker took 5.00 seconds, and it finished 5.00 seconds after the test start.
Test finished after 5.00 seconds.

因为你调用的API是异步的，所以Parallel。每个版本都没有多大意义。你不应该在WaitAll版本中使用. wait，因为这会失去并行性。如果调用者是异步的，另一个选择是使用Task。执行Select和ToArray生成任务数组后的WhenAll。第二种选择是使用Rx 2.0

所有的答案都是为了运行相同的函数。

下面的代码用于调用不同的函数。只需要把你常规的Task.Run()放在一个数组中，然后调用Task.WhenAll():

await Task.WhenAll(new Task[] { 
    Task.Run(() => Func1(args)),
    Task.Run(() => Func2(args))
});

这个问题已经10年了，OP问的是c# 5。

到今天为止，还有一个选择:并行。在。net 6中引入的ForEachAsync方法。

下面是一个基于OP代码的例子:

int[] ids = new[] { 1, 2, 3, 4, 5 };
await Parallel.ForEachAsync(ids, async (i,token) => await DoSomething(1, i, blogClient));

这是完全异步的，不会阻塞任何线程。

此外，它可能比Task更好。WaitAll和Task。WhenAll接近，因为它们不限制并行运行的线程数量。如果你有一个巨大的数组，它会消耗掉你所有的RAM。平行的。ForEachAsync允许你像这样指定并行度:

var options = new ParallelOptions { MaxDegreeOfParallelism = 4 };

await Parallel.ForEachAsync(ids, options, async (i,token) => await DoSomething(1, i, blogClient));

通过这种方式，只有4个线程并行运行。

int[] ids = new[] { 1, 2, 3, 4, 5 };
Parallel.ForEach(ids, i => DoSomething(1, i, blogClient).Wait());

尽管您将这些操作与上面的代码并行运行，但此代码将阻塞每个操作所运行的每个线程。例如，如果网络调用需要2秒，每个线程挂起2秒，不做任何事情，只是等待。

int[] ids = new[] { 1, 2, 3, 4, 5 };
Task.WaitAll(ids.Select(i => DoSomething(1, i, blogClient)).ToArray());

另一方面，上面带有WaitAll的代码也会阻塞线程，在操作结束之前，线程将无法自由处理任何其他工作。

推荐的方法

我更喜欢WhenAll，这将在并行异步执行您的操作。

public async Task DoWork() {

    int[] ids = new[] { 1, 2, 3, 4, 5 };
    await Task.WhenAll(ids.Select(i => DoSomething(1, i, blogClient)));
}

事实上，在上面的例子中，你甚至不需要等待，你可以直接从方法中返回，因为你没有任何延续: DoWork() ｛ Int [] id = new[] {1,2,3,4,5}; 返回Task.WhenAll (id。Select(i => DoSomething(1, i, blogClient)); ｝

为了支持这一点，这里有一篇详细的博客文章 使用ASP的并发异步I/O的方式和位置。NET Web API

我只是想在上面所有的答案中补充一点， 如果你写一个库，使用ConfigureAwait是一个很好的实践(false) 得到更好的性能，就像这里说的。

所以这个片段似乎更好:

 public static async Task DoWork() 
 {
     int[] ids = new[] { 1, 2, 3, 4, 5 };
     await Task.WhenAll(ids.Select(i => DoSomething(1, i))).ConfigureAwait(false);
 }

这里有一个完整的小提琴链接。