Question

I am quite new to work with Reactive Extensions, so this might be a newbie question, but i have the following scenario:

I fetch 3 IEnumerable lists (of different types) from the database and populate a view model. I would however like to coordinate the subscriptions to trigger something when all lists have completed loading. Is this possible with Reactive Extensions or am i thinking in the wrong way? Code loks like this:

GetCustomers()
    .ToObservable(Scheduler.Default)
    .Buffer(20).ObserveOn(SynchronizationContext.Current)
    .Subscribe(View.Model.AddRange);
GetCountries()
    .ToObservable(Scheduler.Default)
    .Buffer(20).ObserveOn(SynchronizationContext.Current)
    .Subscribe(View.Model.AddRange);
GetTransports()
    .ToObservable(Scheduler.Default)
    .Buffer(20).ObserveOn(SynchronizationContext.Current)
    .Subscribe(View.Model.AddRange);

Answer 1

You could try using observable joins. Something like this:

var plan =
    Observable.Start(() => GetCountries())
        .And(Observable.Start(() => GetCustomers()))
        .And(Observable.Start(() => GetTransports()))
        .Then((countries, customers, transports)
            => new { countries, customers, transports });

var query =
    Observable.When(new [] { plan });

query
    .Subscribe(cct =>
    {
        View.Model.AddRange(cct.countries);
        View.Model.AddRange(cct.customers);
        View.Model.AddRange(cct.transports);
    });

It runs in parallel and you get all the results in one at the end.