ReactiveUI: Can't get code to run on background thread

问题

Just dabbling with RxUI and trying to get a noddy example to work...

I've got a WPF view with a ListBox and a button. When I press the button (Go) I want to run a method on a background thread and have the results it produces be added to the ListBox. I'm logging the thread id to check what's executing where. The problem is I always see all the operations happening on the same thread. I've tried specifying Scheduler.Default on the CreateAsyncObservable but then nothing gets added to the ListBox.

public class MainViewModel : ReactiveObject
{
    public MainViewModel()
    {
        Results = new ReactiveList<string>();

        var seq = ReactiveCommand.CreateAsyncObservable(_ => GetAsyncResults());

        seq.ObserveOn(Scheduler.CurrentThread);

        seq.Subscribe(s =>
        {
            Results.Add(string.Format("{0} thread {1}", s, Thread.CurrentThread.ManagedThreadId));
        });

        Results.Add(string.Format("main thread {0}", Thread.CurrentThread.ManagedThreadId));

        Go = ReactiveCommand.Create();
        Go.Subscribe(_ => seq.Execute(null));
    }

    public static IObservable<string> GetAsyncResults()
    {
        Thread.Sleep(1000);
        return (new[] {"Rod", "Jane", "Freddy"}).ToObservable();
    }

    private readonly ObservableAsPropertyHelper<List<string>> _strings;
    public List<string> Strings {get { return _strings.Value; }}

    public ReactiveCommand<object> Go { get; protected set; }

    public ReactiveList<string> Results { get; set; }
}

回答1:

Rx doesn't switch threads until you ask it, and GetAsyncResults simply returns a list of items synchronously. You need to specify RxApp.TaskpoolScheduler to move stuff to a background thread.

public static IObservable<string> GetAsyncResults()
{
    return (new[] {"Rod", "Jane", "Freddy"}).ToObservable(RxApp.TaskpoolScheduler);
}

seq.ObserveOn(Scheduler.CurrentThread);

You didn't use the return value of this, so it doesn't do anything

Go = ReactiveCommand.Create();

Why are you creating two separate commands here?

来源：https://stackoverflow.com/questions/25123992/reactiveui-cant-get-code-to-run-on-background-thread

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reactiveui