Creating Multiple Timers with Reactive Extensions

Question

I\'ve got a very simple class that I am using to poll a directory for new files. It\'s got the location, a time to start monitoring that location, and an interval (in hours

Answer 1

Hmmm. Does DoWork produce a result that you need to do something with? I'll assume so. You didn't say, but I'll also assume DoWork is synchronous.

things.ToObservable()
  .SelectMany(thing => Observable
    .Timer(thing.StartTime, TimeSpan.FromHours(thing.Interval))
    .Select(_ => new { thing, result = DoWork(thing.Uri) }))
  .Subscribe(x => Console.WriteLine("thing {0} produced result {1}",
                                    x.thing.Name, x.result));

Here's a version with a hypothetical Task DoWorkAsync(Uri):

things.ToObservable()
  .SelectMany(thing => Observable
    .Timer(thing.StartTime, TimeSpan.FromHours(thing.Interval))
    .SelectMany(Observable.FromAsync(async () =>
       new { thing, result = await DoWorkAsync(thing.Uri) })))
  .Subscribe(x => Console.WriteLine("thing {0} produced result {1}",
                                    x.thing.Name, x.result));

This version assumes that DoWorkAsync will finish long before the interval expires and starts up a new instance and so does not guard against having concurrent DoWorkAsync running for the same Thing instance.