using System;

using System.Diagnostics;

using System.Threading.Tasks;

using System.Threading;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

       PizzaTask().GetAwaiter().GetResult();

    }

​

    static async Task PizzaTask()

    {

        Stopwatch stopwatch = new Stopwatch();

        stopwatch.Start();

        int totalPizza = 10;

        Console.WriteLine("Started preparing " + totalPizza + "  pizza");

        var tasks = Enumerable.Range(0, totalPizza).Select(i => MakePizza(i));

        await Task.WhenAll(tasks);

        stopwatch.Stop();

​

        Console.WriteLine("Finished preparing " + totalPizza + "  pizza");

        Console.WriteLine("Elapsed time: " + stopwatch.Elapsed.TotalSeconds);

​

    }

​

    static async Task MakePizza(int n)

    {

        await PreparePizza(n);

        await BakePizza(n);

    }

​

    static async Task PreparePizza(int n)

    {

        Console.WriteLine("Start preparing pizza " + n);

        await Task.Delay(1000);

        //Thread.Sleep(5000);// synchronous

        Console.WriteLine("Finished preparing pizza " + n);

    }

​

    static async Task BakePizza(int n)

    {

        Console.WriteLine("Start baking pizza " + n);

        await Task.Delay(1000); // asynchronous 

        //Thread.Sleep(15000); // synchronous 

        Console.WriteLine("Finished baking pizza " + n);

    }

}