using System;

using System.Collections.Generic;

using System.Threading.Tasks;

​

public class Program

{

    private static async Task DoAsyncThing(int i)

    {

        Console.WriteLine("Process1"+i.ToString());

        int x = new Random(5000).Next(0,1000);

        await Task.Delay(x);

        Console.WriteLine("Processed1  done"+i.ToString());

    }

    private static async Task DoAsyncThing2(int i)

    {

        Console.WriteLine("Process thing2 "+i.ToString());

        int x = new Random(2000).Next(0,1000);

        await Task.Delay(x);

        Console.WriteLine("Processed thing2 done"+i.ToString()+" for "+x.ToString());

    }

​

    private static async Task SaveAll()

    {

        Console.WriteLine("Saving All");

        await Task.Delay(1000);

    }

​

    public static async Task ProcessAll()

    {

        var tasks = new List<Task>();

        for (int i = 0; i < 10; i++)

        {

            tasks.Add(DoAsyncThing(i));

            tasks.Add(DoAsyncThing2(i));

        }

​

        await Task.WhenAll(tasks);

        Console.WriteLine("Next Batch");

        await SaveAll();

        Console.WriteLine("Saved");

    }

​

    public static void Main()

    {

        ProcessAll().Wait();

        Console.WriteLine("sdf");

    }

}