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 async Task 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 },

            };

​

​

            await RunTasksWithWhenAll(workers);

​

            Console.WriteLine(Environment.NewLine);

            await RunTasksWithWhenAllAsync(workers);

​

            Console.ReadKey();

        }

​

        private static async Task RunTasksAwaitEachOne(List<Worker> workers)

        {

            var startTime = DateTime.Now;

            Console.WriteLine("Starting test: await");

            foreach (var worker in workers)

            {

                await worker.DoWork(startTime);

            }

            var endTime = DateTime.Now;

            Console.WriteLine("Test finished after {0} seconds.\n",

                (endTime - startTime).TotalSeconds.ToString("F2"));

        }

​

        private static async Task RunTasksWithWhenAllAsync(List<Worker> workers)

        {

            var startTime = DateTime.Now;

            Console.WriteLine("Starting test: Task.WhenAllWithAsync");

​

            var tasks = workers.Select(async worker => await worker.DoWork(startTime));

            await Task.WhenAll(tasks);

​

            var endTime = DateTime.Now;

            Console.WriteLine("Test finished after {0} seconds.\n",

                (endTime - startTime).TotalSeconds.ToString("F2"));

        }

​

        private static async Task RunTasksWithWhenAll(List<Worker> workers)

        {

            var startTime = DateTime.Now;

            Console.WriteLine("Starting test: Task.WhenAllWithoutAsync");

​

            var tasks = workers.Select(worker => worker.DoWork(startTime));

            await Task.WhenAll(tasks);

​

            var endTime = DateTime.Now;

            Console.WriteLine("Test finished after {0} seconds.\n",

                (endTime - startTime).TotalSeconds.ToString("F2"));

        }

​

        static Task PerformTest_TaskWhenAll(List<Worker> workers, DateTime testStart)

        {

            return Task.WhenAll(workers.Select(worker => worker.DoWork(testStart)));

        }

    }

}