In this session, John Papa talked about Silverlight application development patterns such as composite applications with Prism, developing using the Model-View-ViewModel (MVVM) pattern, and methods of implementing large, modular, multi-page applications within your team. Also he talked about frameworks created to help assist in rapid development using these patterns without sacrificing good application development patterns.
MVVM is a pattern, there is no specific way to do it right. Also with Silverlight.
MVVM, MVC, MVP and MV??? are all commonly accepted patterns for maintainable, scalable and testable applications. People look for patterns to describe common way for programming UI.
MVVM is a separation of concerns. Provides loosely coupled UI from logic, good for testing.
Model
The model represents the data, it only a data entity. Not required to know where it gets its data from. Easy to test and to maintain.
ViewModel
Main source of logic for the MVVM triad. It connects the Model to the View. It abstracts the View and provide public properties to be bond with the view. This separation is great for unit testing.
MVVM Variations
View First – ViewModel is declared as Static Resource in the View’s XAML. Works well in Expression Blend. Another way is to create ViewModel in the View’s code-behind.
ViewModel First – view is injected into the ViewModel’s constructor. For example, ViewModel is created first then view is bound with the ViewModel.
View and ViewModel using Intermediary
An intermediary creates both the view and view model, then connect them together.
Prism 2
Prism is set of options, you can use what you want and ignore the rest. In the MVVM case you can just use the module catalog but ignore the Event Aggregator.
The rest of the session was what is prism and how to use it. So I’ll save you the pain.