using System;

using System.Linq;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var task1 = Task1(2);

        var task2 = Task2(5);

        var task3 = Task3(3);

        var allTask = new List<Task<int>> { task1, task2, task3 };

        Parallel.ForEach(allTask, async (task) =>

        {

            var result = await task;

            switch (result)

            {

                case 1:

                    Console.WriteLine("task 1 finished");

                    break;

                case 2:

                    Console.WriteLine("task 2 finished");

                    break;

                case 3:

                    Console.WriteLine("task 3 finished");

                    break;

            }

        });

        Thread.Sleep(6);

    }

    static async Task<int> Task1(int delay)

    {

        await Task.Delay(delay);

        return 1;

    }

    static async Task<int> Task2(int delay)

    {

        await Task.Delay(delay);

        return 2;

    }

    static async Task<int> Task3(int delay)

    {

        await Task.Delay(delay);

        return 3;

    }

}