Presentation ModelThe First Contact

Agenda

Quick Introduction Why should I care about it? View Model XAML Data Binding ViewModel Base Commands Validation Data Templates Resource Systems MVVM Framework How do I do…?

Quick Introduction: Presentation Patterns

UI Patterns Comparison

Passive View Supervising Controller Presentation Model

Presentation Model

“Probably the most annoying part of the Presentation Model is the synchronization between Presentation Model and view. It’s simple code to write, but I always like to minimize this kind of boring repetitive code.Ideally some kind of framework could handle this, which I’m hopping will happen some day with technologies like .NET’s data binding.”

Martin Fowler, 2004.

Model – View – ViewModel

Technology specific implementation of the PM Separation of Markup and Code Behaviour of the Application Look and Feel Tool Support

“Once a developer becomes comfortable with WPF and MVVM, it can be difficult to differentiate the two. ”. Josh Smith, MVVM Guru

Why should I care about it?

Order vs. Chaos Technology Choice Loose Coupling Testability (DEMO) Maintainable Code Blendability (DEMO) It is cool

<Disclaimer>

No Solution is Perfect Different Approaches

View-Centric ViewModel Centric

</Disclaimer>

View Model

Separation of Concerns Enables code reuse State + Operations Provides a Bindable Surface Not Dependent on the View Typically One-To-One ViewModel to View

One-To-Many is very common though

XAML

Humble View Plays nicely with Data Binding

capabilities

Data Binding

Binding Expression Binding Direction Binding to Elements Binding to Templates RelativeSource

DEMO

Commands

Delegate Command vs. Relay Command (DEMO) Uses WPF Behaviours capabilities Map Events to Commands (DEMO)

DEMO

Validation

Implemented on ViewModel, not in Model Class

DEMO

Messaging

Uses a light message bus to communicate between components Publish/Subscribe Frameworks (MVVM Light) (DEMO)

DEMO

MVVM Light Toolkit

ViewModel Locator

Repository of ViewModels Uses WPF DataTemplate Capabilities One View per ViewModel MVVM Light

DEMO

MVVM Light Toolkit

Trade-Offs

Agregate Model vs Proxy Property Start animation on the View through ViewModel How to close a window Clean and Shutdown Handle Navigation Add your own topic to be discussed…

And continues…

Not used only with WPF/Silverlight: ASP.NET MVC Knockout.js Java frameworks (RLY?)

To Far and Beyond… That’s it ;-)