using System;

using System.Collections.Generic;

using System.Threading.Tasks;

using System.Linq;

​

Console.WriteLine("Hello, World!");

​

var numbers = Enumerable.Range(1, 10);

​

var tasks = new List<Task>();

​

​

// Slower: 

foreach (var number in numbers)

{

    await DoubleTheNumber(number);

}

​

​

// Faster:

foreach (var number in numbers)

{

    tasks.Add(DoubleTheNumber(number));

}

//await Task.WhenAll(tasks);

​

​

async Task DoubleTheNumber(int number)

{

    await Task.Delay(1000);

    Console.WriteLine(number*2);

}