รันงานพร้อมกันด้วย WhenAll

using System;
using System.Threading.Tasks;
class Program
{
    static async Task<int> Fetch(int value) { await Task.Delay(20); return value; }
    static async Task Main()
    {
        int[] results = await Task.WhenAll(Fetch(20), Fetch(22));
        Console.WriteLine(results[0] + results[1]);
    }
}