Silverlight 5 MVVM Best Practices

Silverlight 5 MVVM Best Practices

Seeing as how MVVM is being highly regarded as a good system design pattern, I thought I might just jump aboard and give MVVM a shot.

Just a little background about myself before I begin with questions:

I have done a few years of development with ASP.NET Webforms. I have also done a fair bit of development in ASP.NET MVC, which I am quite comfortable with.

Currently, we have a number of "backbone" applications written using ASP.NET MVC 3 which we customize and sell to our clients whenever we're approached. These applications are all meant for internal use, hence plug-ins wouldn't be much of a problem.

The real problem with development is that for large scale business applications with complex business rules, ASP.NET MVC tends to slow us down (writing jQuery / javascript > server side processing > return result, use jQuery to notify > alter view, something along this line).

Then I began looking for answers that will help us improve our time to delivery and also responsiveness (well, we all know how JavaScript is capable of killing us) and my search brought me to Silverlight (we have the time to change, no worries there).

So here comes the questions:

1. I have come across many Silverlight MVVM samples online, but all of them show applications as simple as interacting with only one Database table. Is MVVM pattern well suited for large applications?
2. In MVC, I'm used to Dependency Injection from Ninject to pass an implementation of UnitOfWork to my Controller. In all samples I found online, none of them use any form of DI. Is it really unnecessary? Since the idea of MVVM is to decouple, so why not also decouple ViewModel from Model?
3. I've gone through a book published by Jeremy Likness called Designing Silverlight Business Applications. He used MEF to do the decoupling, which I think doesn't really fit into our application. We do not really need to do "hot-plugging". What's your take on this?
4. MVVM is all about Commands, Databindings and No Code-behinds. What if I want to interact with UIs that do not expose to commands? (I'm not too sure about this, I'm guessing ListView OnSelectionChange?)

Answers & Comments...

Answer: 1

I have no answers for all your answers (never used MEF) but I can tell you my experience:

1- I've been in the development of a quite-large silverlight application and MVVM fits perfect to have a maintainable application. The bigger problems we had because of application size were because of Silverlight, not MVVM 8-)

2- I haven't used it too much but it's useful in many cases. There are several toolkits to use DI with Silverlight like MVVM Light Toolkit: http://compiledexperience.com/blog/posts/blendable-mvvm-dependency-injection-and-unit-testing

4- For interaction between UIs you can use the Mediator pattern. The same MVVM Light Toolkit has a Messenger to subscribe, send and receive messages and maitain every layer decoupled.

Hope this helps you ;-)

by : zapicohttp://stackoverflow.com/users/694693

Answer: 2

To add to the previous answer:

1. We are developing a large corporate-wide Silverlight platform and a set of applications using MVVM. Seems to be working pretty well.

2. We are using DI extensively. Our system is built on top of Prism. Prism contains a large amount of sample applications of various complexity illustrating the use of DI in MVVM.

3. We use Unity as our IoC container. Prism contains guidance for both MEF and Unity. Unity seems to be a more traditional IoC approach.

4. In the vast majority of cases using Bindings and Commands covered our needs. For the others we use Expression Triggers and Actions. You can also create custom Triggers/Actions if necessary.

by : borishttp://stackoverflow.com/users/874831

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