In about 2 weeks now, I’ll have the chance to be part of the French TechDays in Paris as a speaker. This year, I’ll own a session called “Windows Phone performance analysis & optimisation” with my colleague Charlotte.

The agenda looks like the following:

• why performance analysis ?
• device vs emulator
• leveraging WP7 threads
• using the VS profiler for WP7
• tips and tricks

During the session we will use a “real” app we’re working on for a few months now (I’ll share more details after the session). We have some cool tips that haven’t been shared anywhere before, so if performance is a topic of interest for you, stat tuned !

Click on the following image for a link to the TechDays website:

I’m planning to share the most of the content of this session on my blog soon after the event.

Don’t hesitate to stop by and say hi…

Visual Studio 2010 introduced 2 new design time properties: d:DesignInstance and d:DesignData. Those properties can be used in order to specify a design time DataContext in order to have more help during the creation of a binding.

For example, when you create a binding using the Property dialog of VS2010 you can browse your DataContext to select the right property (image from this blog post from Karl Shifflet):

Resharper 6.1 is now able to use those metadata in order to improve the experience you have while typing XAML (which I personally do a LOT!). Here is how it works:

• you create a new ViewModel with a simple property (this property has just get/set because we don’t need much more in the context of this post…)

• you setup a binding in your view

At this point the ReSharper magic comes into play…

• ReSharper warns you the DataContext is unknown

• Offer the ability to fix this

• Note that like in C#, you can very easily resolve namespace issues

• Then notice that the warning is gone (the Title property is no longer underlined)

• You can now add a new binding

• You can then ask ReSharper to create the property in your ViewModel

• Choosing the first option will get you to the ViewModel definition

Now that I’ve upgraded my installation to version 6.1, I think this is a must have !

That’s all for today ! Hope it helps

Next Wednesday (November 9th), I’ll be at the Microsoft Days 11 as a member of the Ask The Expert team. I’ll be playing with the Samsung Slate I got at //BUILD/, discussing WPF, Silverlight, Windows Phone 7 and Windows 8.

Don’t hesitate to stop by and say hi if you’re coming to this event !

This blog post is part of my BUILD series.

I’m having a very busy week here in Anaheim ! I’m meeting many new people and had the chance to enjoy the conference from the inside. I’m also playing with this new Windows 8 slate Microsoft gave us ! I’m not going to do a blog post trying to summarize everything because there is just so much to say.I’m going to try to share my point of view on what I’ve seen here.

Our new platform

The original picture shown during the keynote to introduce the new platform was this one:

There has been a lot of confusion about that because of having XAML with C# in the Metro Style Apps without any reference to the CLR… Doug Steven did a pretty great job (blog post is here) by discussing with key people from the engineering team of Microsoft and creates this new more accurate picture:

Here is a quick summary:

• there is only one CLR
• .Net framework 4.5 is used in both Metro apps and Classic apps
• it’s the same MSIL for Metro apps and Classic apps
• in the Metro platform, we have a subset of the .Net framework (for example no OpenFileDialog…)

New opportunities

Before //BUILD we had already many choices to choose our development environment. we now have even more:

• WPF and managed code for classic desktop apps
• Silverlight in a web environment
• Silverlight out of browser
• WinRT + XAML for Metro apps
• WinRT + HTML for Metro apps

I personally think that Silverlight in a web browser has not a great future. Microsoft just announced for example that the immersive version of IE will not run any plugins (so no Silverlight in the Metro UI) and we ‘ll know Microsoft is pushing HTML5 very strongly.

For classic desktop apps we have 2 options: WPF and Silverlight. Each of them has advantages and the choice we’ll have to do will depend on our constraints (deployment, business needs, connectivity…). I think there is room for the 2 platforms there.

For the Metro UI, you can choose between XAML and HTML. Microsoft told us they will keep a good feature parity between the 2 options. If you choose XAML and managed code you’ll be able to leverage a subset of the .Net framework.

I think another important aspect is that Metro will be available on Windows 8 only. Even though this new version of the OS might have a fast deployment rate (thanks to the slates), in many companies I don’t think it will be that fast.This, plus the fact that some LOB apps will not benefit the Metro UI leaves a lot of work to do in the desktop applications world (where we have both WPF and SL)… For WPF, we now have a new version coming in .Net 4.5. You can check out the new stuff here in the documentation.

In my next blog post I’m going to try to go deeper in the new WinRT/XAML world and see how it looks like for us, WPF and Silverlight developers.

Here is the top 5 of MVVM frameworks supporting WPF, Silverlight and Windows Phone 7:

1. MVVM Light (61k downloads)
2. nRoute (19k downloads)
3. Caliburn Micro (18k downloads)
4. Simple MVVM toolkit (5k downloads)
5. Catel (5k downloads)

Today, I’d like to share with you a simple concept I try to stick to when I’m doing WPF, Silverlight or Windows Phone 7 development. It can be summarized as “Enough ViewModel is enough”.

The simple idea behind this slogan is that there ARE stuff which are view-related and SHOULD NOT be embedded in the ViewModel layer. I’ve seen too many developers going the “100% viewmodel way” which means for them absolutely no code-behind without any dispensation.

For example, I came across this code. It’s the ViewModel layer associated to a simple view where the user fills various input and has immediate feedback about the progress (like “75% of the fields are completed”). If by the way you’re interested in implementing this behavior you can check out this article I wrote on CodeProject)

The following code is simplified to the sake of the article:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57

public class ViewModel
{
    // data field acts as the model object behind the VM layer
    private Data data;
 
    // missing code...
    // public properties used by the view using databinding
 
    public ViewModel()
    {
        // very simplified for this article...
        this.data = new Data();
        this.data.SelectedValuesChanged += new EventHandler(data_SelectedValuesChanged);
    }
 
    public void UpdateProgress()
    {
        // some code...
    }
 
    void data_SelectedValuesChanged(object sender, EventArgs e)
    {
        this.UpdateProgress();
        this.Initialize();
    }
 
    public void Initialize()
    {
        var item = this.data.GetItem("id1");
        if (item != null)
        {
            item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
            item.SelectedValuesChanged += new EventHandler(item_SelectedValuesChanged);
            foreach (var value in item.Values)
                value.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
        }
 
        item = this.data.GetItem("id2");
        if (item != null)
        {
            item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
            item.SelectedValuesChanged += new EventHandler(item_SelectedValuesChanged);
            foreach (var value in item.Values)
                value.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
        }
    }
 
    void item_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        this.UpdateProgress();
    }
 
    void item_SelectedValuesChanged(object sender, EventArgs e)
    {
        this.UpdateProgress();
    }
}

The idea is simple, as soon as the user changes a value in the View, we must compute the current progress. Because the ViewModel have several levels, we end-up having to register to every single PropertyChanged event which leads to cumbersome code. By the way, this code can also creates memory leaks since we register a lot of event handlers without removing them, but that’s another discussion…

Here is my way to solve this problem:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

public partial class View : UserControl
{
    private readonly ViewModel viewmodel;
 
    public View()
    {
        InitializeComponent();
 
        this.viewmodel = new ViewModel();
 
        this.AddHandler(
            FocusManager.LostFocusEvent,
            new RoutedEventHandler(this.OnLostFocus),
            true);
    }
 
    private void OnLostFocus(object sender, RoutedEventArgs e)
    {
        this.viewmodel.UpdateProgress();
    }      
}

What is wrong with this way ? The View has code-behind ? That’s not a big deal: the code is more readable, maintainable. It makes also more sense: when a view-related operation occurs (in this case, focus has changed), update the progress.

The simple message I’d like to spread is the fact that there is nothing wrong with the fact to have sometime, a little bit of code-behind in your view if that facilitates your architecture. There is no need to create a complicated infrastructure with behaviors, commands or bindings just to keep the view empty if that does not make sense.

Another great example in a real application is available in the Advanced MVVM book by Josh Smith.

This is the part 2 of my post about today’s Mix keynote – first one is about Windows Phone 7 improvements. Now let’s talk about Silverlight 5 !

New features:

• Multiple Windows support (for Out Of Browser scenarios)
• Ancestor RelativeSource binding
• Implicit DataTemplates
• ClickCount for mouse events
• Binding on Style setter
• Realtime sound (low-latency audio)
• Variable speed playback
• Linked text containers
• Custom markup extensions
• XAML binding debugging
• 3D graphics API (based on XNA)

Other features

• HW video decode for H.264
• Multi-core background JIT
• Improved graphic stacks
• XAML parser performance improvements
• Network latency optimizations
• Text layout performance improvements

Download everything you need right now: http://www.silverlight.net/getstarted/silverlight-5-beta/

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:

1
2
3
4
5
6
7
8
9
10
11
12
13
14

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))
                .TakeUntil(this.GetMouseLeftButtonUpObservable())
                .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:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

this.textbox.GetTextChangedObservable()
    .DistinctUntilChanged((ea) => this.textbox.Text)
    .Throttle(TimeSpan.FromMilliseconds(300))
    .ObserveOnDispatcher()
    .Do(ea => this.ShowLoadingIndicator())
    .Select(ea => TweeterHelper.Search(this.textbox.Text))
    .Switch()
    .ObserveOn(Scheduler.Dispatcher)
    .Select(page => TweeterHelper.ParseTwitterSearch(page))
    .Subscribe((tweets) =>
                    {
                        this.HideLoadingIndicator();
                        this.listbox.ItemsSource = tweets;
 
                        TweeterHelper.LocalizeTweets(this.map, 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:

1
2
3
4
5
6
7
8
9
10

private void MoveEllipse(IObservable<Acceleration> accelerationObservable)
{
    accelerationObservable
        .SlidingBuffer(2)
        .Select(accCouple => new Acceleration(accCouple.First(), accCouple.Last()))
        .ObserveOnDispatcher()
        .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 !

During the next 3 days, the “Palais des Congrès” in Paris will hosting the TechDays 2011. For the very first time, I’ll have the chance to be part of it as a speaker for a talk about Rx (Reactive Extensions).

The session will take place in room 241, tomorrow Thursday 8, from 1pm to 2pm. Here is the link to the session’s description (in French).

I’ll share presentation slides and source code by the end of the week

Besides adding this new framework, I updated the download count for each framework, which allowed me to do some statistics. Here are the download progression for the most popular MVVM frameworks between July 2010 and January 2011:

Top progression during the last 6 months:

1. MVVM Light (by Laurent Bugnion): +160%
2. MVVM Helpers (by Mark Smith): +133%
3. MEFedMVVM (by Marlon Grech): +129%
4. WAF (by Jurgen Berchtel): +150%

Top downloaded frameworks:

1. Caliburn (by Rob Eisenberg): +36 000 downloads
2. MVVM Light (by Laurent Bugnion): +30 000 downloads
3. WAF (by Jurgen Berchtel): +30 000 downloads

Congratulations to their respective authors.