My example of a "metric stream": I have a main thread doing work, and I want to push metrics asynchronously to an external server at a reasonable buffered interval. Seems like the perfect task for Rx :) ...but if I'm not careful, the main thread will tear-down the app before the subscriber finishes its work!

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reactive.Subjects;
using System.Reactive.Linq;
using System.Threading;

namespace MetricPushDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // Scenario: main thread is generating metrics that I want to push asynchronously to an external system

            var subj = new Subject<int>(); // my metric sequence

            // Option 1: standard subscribe is not guaranteed to complete before the main app shuts down
            var option1 = subj
                .ObserveOn(System.Reactive.Concurrency.Scheduler.Default) // make async
                .Buffer(TimeSpan.FromSeconds(3)) // buffer so we don't push too frequently
                .Where(m => m.Any())
                .Subscribe(m =>
                {
                    Thread.Sleep(1000); // simulate slow round-trip

                    Console.WriteLine("Option 1 pushed {0} metrics to external system", m.Count());
                });

            // Option 2 works for me: it returns a task that we can await at the end
            //var option2 = subj
            //    .ObserveOn(System.Reactive.Concurrency.Scheduler.Default) // make async
            //    .Buffer(TimeSpan.FromSeconds(3)) // buffer so we don't push too frequently
            //    .Where(m => m.Any())
            //    .ForEachAsync(m =>
            //    {
            //        Thread.Sleep(1000); // simulate slow round-trip

            //        Console.WriteLine("Option 2 pushed {0} metrics to external system", m.Count());
            //    });

            Console.WriteLine("Do some work");
            subj.OnNext(1);
            Console.WriteLine("Do some more work");
            subj.OnNext(2);
            Console.WriteLine("And some more");
            subj.OnNext(3);
            Console.WriteLine("done");
            subj.OnCompleted();

            //option2.Wait(); // wait for option 2 to complete

            // I welcome your thoughts! :)
        }
    }
}