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Understanding the MVVM pattern. Laurent Bugnion Senior User Experience Integrator IdentityMine http://[www|blog].galasoft.ch http://www.identitymine.com. What is MVVM?. A weird acronym Model – View – ViewModel « MVVM in a SLOOB with SLUT » Woven into WPF/SL Some confusion:
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Understanding the MVVM pattern Laurent Bugnion Senior User Experience Integrator IdentityMine http://[www|blog].galasoft.chhttp://www.identitymine.com
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
The MVC pattern Model View Controller
The Passive View pattern Model View Controller
The Presentation Model pattern Model View DataBinding Presentation Model (ViewModel)
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
Demo Hello MVVM (and Hi Blend)
Bridging the gap View DataBinding Commands Messages ViewModel Model
Bridging the gap View View ViewModel Messages ViewModel View Messages + callback ViewModel
Commands “Point of entry” for a method Can be data bound ICommand interface • Execute method • CanExecute method • CanExecuteChanged event
Messaging Should be simple by default Possible to open filtered channels • To a target Type (or an Interface) • With a Token No constraints at all
Demo Commands and RelayCommands, Messaging
MVVM Light Toolkit “Breaking the monotony” http://www.galasoft.ch/mvvm/getstarted http://mvvmlight.codeplex.com V3 SP1 released with phone support Keep it small Keep it simple
MVVM Light Toolkit ESSENTIALS • RelayCommand • Messenger • ViewModelBase EXTRAS • EventToCommand • DispatcherHelper
MVVM Light Toolkit Project templates (VS + Blend) Item templates (VS + Blend) Code snippets
Demo MVVM Light, Unity, Blendability
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
Debunk 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”
Debunk 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”
Further information http://blog.galasoft.ch http://www.galasoft.ch/mvvm/getstarted http://tinyurl.com/mvvmexplained Twitter: @LBugnion