TechDays 2011: Rx talk, slides and source code

As promised, here is a blog post which shares source code and slides for the Rx talk I gave during last TechDays in Paris. I animated this session with my co-worker Charlotte and with Mitsu.

Download slides here.
Download source code here.

Demo1: Drag’n’drop in a WPF application

The goal was to implement a basic drag’n’drop functionality in a WPF application. The Rx query looks like the following:

var query = from mouseDown in this.image.GetMouseLeftButtonDownObservable()
            let downPosition = mouseDown.EventArgs.GetPosition(this)
            let rect = new Rect(downPosition.X - 10, downPosition.Y - 10, 20, 20)
            let delta = mouseDown.EventArgs.GetPosition(this.image)
            from mouseMove in this.GetMouseMoveObservable()
                .Select(ea => ea.EventArgs.GetPosition(this))
                .SkipWhile(p => rect.Contains(p))
                .DoOnce(p => this.onMouseEnter.Begin(this.image))
                .Select(p => p.Offset(delta))
                .Finally(() => this.onMouseLeave.Begin(this.image))
            select mouseMove;

query.Subscribe(p => this.image.SetPosition(p));

Demo2: online Twitter search and Bing map geolocalization

This time, the goal was to query Twitter asynchronously and to geolocalize the associated Tweets. The Rx query:

    .DistinctUntilChanged((ea) => this.textbox.Text)
    .Do(ea => this.ShowLoadingIndicator())
    .Select(ea => TweeterHelper.Search(this.textbox.Text))
    .Select(page => TweeterHelper.ParseTwitterSearch(page))
    .Subscribe((tweets) =>
                        this.listbox.ItemsSource = tweets;

                        TweeterHelper.LocalizeTweets(, tweets);

Demo3: using the accelerometer in a Windows Phone 7 application

The last demo was about the usage of the accelerometer in a Windows Phone 7 application. Here is the relevant Rx query:

private void MoveEllipse(IObservable accelerationObservable)
        .Select(accCouple => new Acceleration(accCouple.First(), accCouple.Last()))
        .Do(acc => this.textBlock.Text = acc.ToString())
        .Scan(new Point(x0, y0), (point, acc) => point.Move(acc).ClipTo(horizontalInterval, verticaInterval))
        .Subscribe(p => this.ellipse.SetCenter(p));

Doing this session was a really great experience ! I’d like to thank Charlotte and Mitsu for doing it with me. Also, I’d like to thank all users who came to the presentation !

3 thoughts on “TechDays 2011: Rx talk, slides and source code

  1. I love every single post in your blog! Minor point: in some code snippets lambdas are being shown with “=>” instead of “=>”

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