using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

using System.Threading;

public class Program

{

    public static async void Main()

    {

        var runner = new Runner();

        Console.WriteLine("Main1");

        await runner.DoOne();

        Console.WriteLine("Main2");

        await runner.DoTwo();

        Console.WriteLine("Main3");

    }

}

​

public class Runner

{

    public async Task DoOne()

    {

        Console.WriteLine("DoOne1");

        await Task.Delay(2000);

        Console.WriteLine("DoOne2");

    }

    public async Task DoTwo()

    {

        Console.WriteLine("DoTwo1");

        await Task.Delay(500);

        Console.WriteLine("DoTwo2");

    }

}

​