using System;

using System.Collections.Generic;

using System.Threading.Tasks;

​

namespace Stackoverflow

{

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Start");

            Console.WriteLine();

            var srvc = new Service();

            srvc.ConsumeSingleAsync().Wait();

            srvc.ConsumeWithWhenAllAsync().Wait();

            Console.WriteLine();

            Console.WriteLine("Done");

        }

    }

​

    public class Service

    {

        DAL _dal = new DAL();

        public async Task ConsumeWithWhenAllAsync()

        {

            var taskOne = _dal.GetDatesAsync();

            var taskTwo = _dal.GetDatesAsync();

            await Task.WhenAll(taskOne, taskTwo);

            Console.WriteLine("Task One Results");

            foreach (var date in taskOne.Result)

            {

                Console.WriteLine(date);

            }

            Console.WriteLine("Task Two Results");

            foreach (var date in taskTwo.Result)

            {

                Console.WriteLine(date);

            }

        }

        public async Task ConsumeSingleAsync()

        {

            var task = _dal.GetDatesAsync();

            await Task.WhenAll(task);

            Console.WriteLine("Task Results");

            foreach (var date in task.Result)

            {

                Console.WriteLine(date);

            }

            Console.WriteLine();

        }

    }

​

    public class DAL

    {

        public Task<IEnumerable<DateTime>> GetDatesAsync()

        {

            return Task.FromResult<IEnumerable<DateTime>>(new[]

            {

                DateTime.Now, DateTime.Now.AddDays(1), DateTime.Now.AddDays(2), DateTime.Now.AddDays(3)

            });

        }

    }

}