2. Understanding the MVVM pattern
Laurent Bugnion
Senior User Experience Integrator
IdentityMine

3. Model – View – ViewModel « MVVM in a SLOOB with SLUT »
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
View
DataBinding
Presentation Model
(ViewModel)

7. 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)
Demo of connection to WCF service, fails in Blend
Show how to attach to process
Identify problem
IsInDesignMode

9. Bridging the gap
View
DataBinding
Commands
Messages
ViewModel
Model

10. View ViewModel View ViewModel View ViewModel
Bridging the gap
View
ViewModel
View
ViewModel
Messages
View
ViewModel
Messages
+ callback

11. “Point of entry” for a method” Can be data bound ICommand interface
Commands
“Point of entry” for a method”
Can be data bound
ICommand interface
Execute method
CanExecute method
CanExecuteChanged event handler

12. Commands and RelayCommands
Demo of connection to WCF service, fails in Blend
Show how to attach to process
Identify problem
IsInDesignMode

13. RelayCommands
RelayCommand MyCommand = new RelayCommand( () => ..., () => true | false); RelayCommand<T> MyGenericCommand = new RelayCommand<T>( p => ..., p => true | false);

14. Should be simple by default Possible to open filtered channels
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 Demo of connection to WCF service, fails in Blend
Show how to attach to process
Identify problem
IsInDesignMode

16. Messaging
Messenger.Default.Register<T>( this, p => DoSomething(p)); Messenger.Default.Send<T>(p);

17. “Breaking the monotony” http://www.galasoft.ch/mvvm/getstarted
MVVM Light Toolkit
“Breaking the monotony”
V3 released at MIX10
Keep it small
Keep it simple

18. ESSENTIALS RelayCommand Messenger ViewModelBase EXTRAS EventToCommand
MVVM Light Libraries V3
ESSENTIALS
RelayCommand
Messenger
ViewModelBase
EXTRAS
EventToCommand
DispatcherHelper

19. Project templates (VS + Blend) Item templates (VS + Blend)
MVVM Light Tools V3
Project templates (VS + Blend)
Item templates (VS + Blend)
Code snippets

20. MVVM Light Toolkit, Unity, Blendability
Demo of connection to WCF service, fails in Blend
Show how to attach to process
Identify problem
IsInDesignMode

21. INotifyPropertyChanged Commands
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. “No code in the code behind”
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. “I don’t need separation because I don’t have a designer”
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
Demo of connection to WCF service, fails in Blend
Show how to attach to process
Identify problem
IsInDesignMode

25. Thanks @LBugnion http://blog.galasoft.ch
@LBugnion