ReactiveProperty provides execution thread control feature. ReactiveProperty raise PropertyChanged event on UI thread automaticaly.

Change the scheduler

You can change this behavior using IScheduler. When the instance creation time, set IScheduler instance to raiseEventScheduler argument.

var rp = Observable.Interval(TimeSpan.FromSeconds(1))
    .ToReactiveProperty(raiseEventScheduler: ImmediateScheduler.Instance);

ReactiveCollection and ReadOnlyReactiveCollection raise CollectionChanged event on UI thread same as ReactiveProperty. This behavior can be changed using the scheduler constructor and factory method argument.

var collection = Observable.Interval(TimeSpan.FromSeconds(1))
    .ToReactiveCollection(scheduler: ImmediateScheduler.Instance);

var readOnlyCollection = Observable.Interval(TimeSpan.FromSeconds(1))
    .ToReadOnlyReactiveProperty(scheduler: ImmediateScheduler.Instance);

Change the gloabl scheduler

Can change the ReactiveProperty's default scheduler using ReactivePropertyScheduler.SetDefault method.

ReactivePropertyScheduler.SetDefault(TaskPoolScheduler.Default);
var taskPoolRp = new ReactiveProperty<string>();
ReactivePropertyScheduler.SetDefault(ImmediateScheduler.Instance);
var immediateRp = new ReactiveProperty<string>();

taskPoolRp.Value = "changed"; // raise event on the TaskPoolScheduler thread.
immediateRp.Value = "changed"; // raise event on the ImmediateScheduler thread.

Rx operator

Of cource, you can use ObserveOn extension method.

var rp = Observable.Interval(TimeSpan.FromSeconds(1))
    .ObserveOn(someScheduler)
    .ToReactiveProperty();

And we provide ObserveOnUIDispatcher extension method. This is a shortcut of ObserveOn(ReactiveProeprtyScheduler.Default).

var rp = Observable.Interval(TimeSpan.FromSeconds(1))
    .ObserveOnUIDispatcher()
    .ToReactiveProperty();

Limitations

ReactiveProperty was designed for single UI thread platform. It means it doesn't work on the multi UI thread platform which is like UWP platform.

UWP has multi UI thread in the single process when multi Window create. If you create multi-window in UWP, then should set ImmediateScheduler to ReactivePropertyScheduler, when the app was launched. Or use ReactivePropertySlim / ReadOnlyReactivePropertySlim classes.