using System;

using System.Threading.Tasks;

using System.Collections.Generic;

public class Program

{

    public static async Task Main()

    {

        var runner = new Runner();

    try

    {

        await foreach (var element in runner.Run1())

        {

            element.Dump();

            if(element==3){

                throw new ArgumentException();

            }

        }

    }

    catch (Exception ex)

    {

    }

    Console.WriteLine("sum is "+ runner.Sum);

    }

}

​

class Runner

{

​

    public double Sum {get; private set;}= 0;

​

    public async IAsyncEnumerable<int> Run1()

    {

        var y = Run2();

        await foreach (var element in y)

        {

            Sum += element;

            yield return element;

        }

    }

​

    private async IAsyncEnumerable<int> Run2()

    {

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

        {

            await Task.Delay(10);

            yield return i;

        }

    }

​

}