Should I use the Model-View-ViewModel (MVVM) pattern in Silverlight projects?

Question

One challenge with Silverlight controls is that when properties are bound to code, they\'re no longer really editable in Blend. For example, if you\'ve got a ListView that\'

Answer 1

With the Feb 2009 release of Prism v2 by P&P, even better support for MVVM now available for Silverlight and WPF. See microsoft.com/compositewpf for more details.

Answer 2

I've always thought MVVM and PresntationModel http://martinfowler.com/eaaDev/PresentationModel.html are essentially the same thing. PresentationModel is a lot easier to say. I've used it succesfully in java swing, windows forms, WPF and silverlight. If you think in terms of separation of concerns a Presentation Model makes a lot of sense. You have one class whose only concern is providing a Presentation friendly Model.It really doesn't matter what technology is used to show it on the screen. It might change some implementation details but splitting the concerns apart is a good idea no matter how you show the information. Because of that separation you can easily write tests against your presentation model regardless of the view technology. So that's a plus.

Answer 3

I think many of us are waiting for the trailblazers to go ahead and create really good sample apps using MVVM in Silverlight (and WPF for that matter). There are a number of tricky areas such as the lack of ICommand in Silverlight, or the difficulty of interacting with animations starting and stopping only using data binding.

Its definitely a pattern to watch for the future though, and is worth trying out if you don't mind 'cheating' occasionally in the places where you can't quite figure it out.

Answer 4

I agree with Jonas. MVVM seems to be the model that works best for me (though John Papa thinks MVP makes more sense). I have an MSDN Article on this coming out in March that hopefully will answer the call for a good example.

BTW, I would like to see some cohesion in the MVVM Framework department. There isn't a good solution for a framework to follow yet. I like Jonas' (I think Jonas' is the FX Framework) but since its not WPF compatible it might not be the right choice for some.

Answer 5

There's a very good Techdays 2010 video introduction to the MVVM pattern, clearly explained:

• TechDays 2010: Understanding the Model-View-ViewModel pattern
• Hanselminutes podcast by Laurent

For more complicated applications that require a higher degree of automated testing it definitely makes sense, and the move away from DependencyProperties to DataContext binding is a lot neater than it's ASP.NET counterpart.

The biggest challenge I've found with Silverlight is testing the actual UI (there's one commercial framework so far I think), and the huge tangle of event calls you get into when using WCF services (or the WebClient for that matter) with Silverlight.

Answer 6

I've been using MVVM lately on a couple of different Silverlight projects and it's been working really well, I would definitely recommend it. Jonas's post is a great place to start, I've recently blogged on my MVVM experiences too and created a really simple solution to demo the main touch points.