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Source: Dan Wahlin's WebLog

For those that didn’t make it to the presentation, I’ve included the slides and code in this post (download below). Topics covered in the slides and code include:

• The benefits of using the MVVM Pattern
• The Role of a ViewModel class
• Creating a ViewModelBase class for common functionality
• Creating a ViewModel class
• Using a Service Agent class
• Adding commanding into a Silverlight application
• Using commanding with non-ButtonBase controls
• The role of messaging
• MVVM Frameworks

Source: Dan Wahlin's WebLog

Developing Silverlight applications has always been something I've enjoyed. I'm a big fan of the data binding engine that the framework provides and like the flexibility that XAML provides for building user interfaces. With all of the benefits Silverlight provides, the process of developing Silverlight applications hasn't always been as smooth as it could be especially if you relied solely on Visual Studio in the past. Silverlight 2 provided a read-only Visual Studio designer that didn't provide much in the way of functionality while Silverlight 3 only allowed XAML to be edited directly in the editor. Developers using Expression Blend weren't affected by Visual Studio designer limitations much while those without it ended up creating a lot of XAML by hand.

Data validation is an important part of any application. If you've written code to validate data in Silverlight applications prior to the release of Silverlight 4, you've probably discovered that there isn't a great way to ensure that data is entered correctly and errors displayed properly by controls. The typical technique used for validating data was to throw exceptions within property setter blocks as data was found to be invalid. Controls bound to a property could be notified of a data validation exception by setting ValidatesOnExceptions to true in the data binding. Although this technique certainly works, there are some new options available in Silverlight 4 that can be used without resorting to throwing exceptions.

Due to time constraints I ended up switching to 100% demos in the afternoon session so we could get through all the content in a day which worked out well and allowed us to cover a lot of ground in 6 hours. There were several different groups there from Microsoft such as DPE, devs from various product groups as well as different services groups such as MCS. Thanks to everyone in attendance for the great questions and interaction during the workshop. I enjoyed talking with everyone about the ways they were using Silverlight 4 within Microsoft and externally with customers. 

There are several different topics I could cover related to "lessons learned" (some of them were more painful than others) but I'll keep it to 5 items for this post and cover additional lessons learned in the future. The topics discussed were put together for a TechEd talk:

1. Pick a Pattern and Stick To It
2. Data Binding and Nested Controls
3. Notify Users of Successes (and failures)
4. Get an Agent – A Service Agent
5. Extend Existing Controls

 

Silverlight 4 has a lot of great features that can be used to build consumer and Line of Business (LOB) applications. Although Webcam support, RichTextBox, MEF, WebBrowser and other new features are pretty exciting, I’m actually enjoying some of the more simple features that have been added such as text trimming, built-in wheel scrolling with ScrollViewer and data binding enhancements such as StringFormat. In this post I’ll give a quick introduction to a simple yet productive feature called text trimming and show how it eliminates a lot of code compared to Silverlight 3.

The guest panel answers questions sent in from Twitter about the features in Silverlight 4, thoughts on MVVM, and the panel members' experiences developing Silverlight. This is a great chance to hear from some of the leading Silverlight luminaries.

If you’re building Silverlight applications that consume data then you’re probably making calls to Web Services. We’ve been successfully using WCF along with Silverlight for several client Line of Business (LOB) applications and passing a lot of data back and forth. Due to the pain involved with updating the ServiceReferences.ClientConfig file generated by a Silverlight service proxy (see Tim Heuer’s post on that subject to see different ways to deal with it) we’ve been using our own technique to figure out the service URL. Going that route makes it a peace of cake to switch between development, staging and production environments.

Thanks to everyone who attended my sessions at DevConnections Las Vegas. I had a great time meeting new people, discussing business problems and solutions and interacting. Here’s the code and slides for the sessions.  For those that came to the full-day Silverlight workshop I’ve included the slides that didn’t get printed plus a ton of code to help you get started with various Silverlight topics.