RxExtensions Observable.FromAsync

RxAsync.cs

using System;
using System.Reactive.Linq;
using System.Reactive.Subjects;
using System.Threading.Tasks;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {
            var sbj = new Subject<int>();

            var subscription1 = sbj.Select(t => Observable.FromAsync(DoStuffAsync)).Concat()
                .Do(r=>
                {
                    Console.WriteLine($"{DateTime.Now.TimeOfDay.Seconds} Subscription 1 : {GetCurrentThread()}");
                })
                .Subscribe();
            var subscription2 = sbj.Select(t => Observable.FromAsync(DoStuffAsync)).Concat()
                 .Do(r => 
                 {
                     Console.WriteLine($"{DateTime.Now.TimeOfDay.Seconds} Subscription 2 : {GetCurrentThread()}");
                 })
                 .Subscribe();

            for (int i = 0; i < 10; i++)
            {
                sbj.OnNext(i);
                Console.WriteLine($"{DateTime.Now.TimeOfDay.Seconds} Next {i} : {GetCurrentThread()}");
            }

            Console.ReadLine();
        }

        static async Task DoStuffAsync()
        {
            await Task.Delay(2000);
        }

        static int GetCurrentThread()
        {
            return System.Threading.Thread.CurrentThread.ManagedThreadId;
        }
    }
}