Understanding The MVVM Pattern (TechDays Belgium)
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The document discusses the MVVM (Model-View-ViewModel) pattern, its definitions, components, and importance in WPF/Silverlight environments. It covers implementation aspects, including commands, messaging, and the MVVM Light Toolkit, emphasizing testability and design-time data handling. The document also addresses common misconceptions about MVVM and its applicability in various scenarios, including its limitations and flaws.
![Understanding the
MVVM pattern
Laurent Bugnion
Senior User Experience Integrator
IdentityMine
http://[blog|www].galasoft.ch](https://image.slidesharecdn.com/cfakepathtechdaysbugnionunderstandingthemvvmpattern-100402182422-phpapp02/85/Understanding-The-MVVM-Pattern-TechDays-Belgium-2-320.jpg)
Understanding The MVVM Pattern (TechDays Belgium)
- 2. Understanding the MVVM pattern Laurent Bugnion Senior User Experience Integrator IdentityMine http://[blog|www].galasoft.ch
- 3. What is MVVM? • A weird acronym • Model – View – ViewModel • « MVVM in a SLOOB with SLUT » • Woven into WPF/SL • Some confusion: • MVVM is really just the pattern • The rest are helpers, practices, etc
- 4. The MVC pattern Model View Controller
- 5. The Passive View pattern Model View Controller
- 6. The Presentation Model pattern Model View DataBinding Presentation Model (ViewModel)
- 7. Blendability • Testability, Maintainability, Blendability • “The ability to be edited in Blend” • (and Visual Studio designer…) • Differentiate code in design and runtime • Create design time data
- 8. Hello MVVM (and Hi Blend)
- 9. Bridging the gap View DataBinding Commands Messages ViewModel Model
- 10. Bridging the gap View View Messages ViewModel ViewModel View Messages + callback ViewModel
- 11. Commands • “Point of entry” for a method” • Can be data bound • ICommand interface • Execute method • CanExecute method • CanExecuteChanged event handler
- 13. RelayCommands RelayCommand MyCommand = new RelayCommand( () => ..., () => true | false); RelayCommand<T> MyGenericCommand = new RelayCommand<T>( p => ..., p => true | false);
- 14. Messaging • Should be simple by default • Possible to open filtered channels • To a target Type (or an Interface) • With a Token • With various Messenger instances • No constraints at all
- 15. Messaging
- 16. Messaging Messenger.Default.Register<T>( this, p => DoSomething(p)); Messenger.Default.Send<T>(p);
- 17. MVVM Light Toolkit • “Breaking the monotony” • http://www.galasoft.ch/mvvm/getstarted • http://mvvmlight.codeplex.com • V3 released at MIX10 • Keep it small • Keep it simple
- 18. MVVM Light Libraries V3 • ESSENTIALS • RelayCommand • Messenger • ViewModelBase • EXTRAS • EventToCommand • DispatcherHelper
- 19. MVVM Light Tools V3 • Project templates (VS + Blend) • Item templates (VS + Blend) • Code snippets
- 21. Flaws of MVVM • Too much code needed • INotifyPropertyChanged • Commands • Some operations are tricky (set focus…) • Not applicable to ASP.NET, etc • Message to community is not clear
- 22. Debunking the myths • “No code in the code behind” • “If you put code in the View's code-behind, the MVVM police will take your family away” • “No need for converters” • “MVVM is only suitable for big projects” • “MVVM costs performance” • “MVVM is complex / makes my head hurt”
- 23. Debunking the myths • “I don’t need separation because I don’t have a designer” • “You cannot use MVVM with other patterns” • “MVVM will make you rich and attractive”
- 24. MVVM on the Windows Phone 7
Editor's Notes
- #9: Demo of connection to WCF service, fails in BlendShow how to attach to processIdentify problemIsInDesignMode
- #13: Demo of connection to WCF service, fails in BlendShow how to attach to processIdentify problemIsInDesignMode
- #16: Demo of connection to WCF service, fails in BlendShow how to attach to processIdentify problemIsInDesignMode
- #21: Demo of connection to WCF service, fails in BlendShow how to attach to processIdentify problemIsInDesignMode
- #25: Demo of connection to WCF service, fails in BlendShow how to attach to processIdentify problemIsInDesignMode