Question

I make this async webrequest call mutliple times(can be twice or thrice or even 6 times depending on conditions)

        var request = HttpWebRequest.CreateHttp(url);

        var observableRequest = Observable.FromAsyncPattern<WebResponse>(
            request.BeginGetResponse, request.EndGetResponse);

        Observable.Timeout(observableRequest.Invoke(), TimeSpan.FromSeconds(120)).
            Subscribe(response => { HandleListResult(response); },
            exception => { HandleListResultTimeOut(exception); });

I have a Collection (List) in the ViewModel which has a Binding to a LisBox and i would like to keep adding to the collection after each response returns.

What is the best practice to make this happen using Reactive Extensions ? Would be great if someone can show me some sample code !

Thanks in advance

Answer 1

You can translate url flow directly into streams:

    public static IObservable<Stream> RequestToStream(
        this IObservable<string> source, TimeSpan timeout)
    {
        return
            from wc in source.Select(WebRequest.Create)
            from s in Observable
                .FromAsyncPattern<WebResponse>(wc.BeginGetResponse,
                    wc.EndGetResponse)()
                .Timeout(timeout, Observable.Empty<WebResponse>())
                .Catch(Observable.Empty<WebResponse>())
            select s.GetResponseStream();
    }

And then you need to observe your responces on UI, you need to use .ObserveOnDispatcher(), f.e.:

        Observable
            .Return("www.msdn.com")
            .RequestToStream(TimeSpan.FromSeconds(1))
            .ObserveOnDispatcher()
            .Subscribe(request => UpdateUI(Request));