This document provides an overview of MVVM (Model-View-ViewModel) pattern including its elements, need, key interfaces like INotifyPropertyChanged and ICommand. It also discusses ObservableCollection, pros and cons of MVVM and frameworks that support MVVM pattern like WPF, Prism, MVVM Light Toolkit.

1. MVVM SESSION

2. CONTENTS
• Prerequisites
• What is MVVM?
• Elements of MVVM
• Architectural Diagram
• Why we need MVVM?
• What is INotifyPropertyChanged Interface?
• What is Icommand Interface?
• Pros & Cons
• Practical Implementation
• Supported Frameworks & References

3. BASICS AND KEY POINTS TO KNOW
• Xaml
• Data Binding
• Key Concepts
1.observablecollection
2.INotifyPropertyChanged
3.ICommand

4. MVVM(MODEL, VIEW, VIEWMODEL)
• is an architectural pattern created by John Gossman from WPF
team
• is a variation of MVC pattern
• Also known as Presentation model
• Woven into WPF/SL
• WPF Data Binding & Commanding

5. ELEMENTS OF MVVM
• Model : Business Logic
• View : UI logic
• ViewModel : Presentational Logic

6. ARCHITECTURAL DIAGRAM

7. NEED OF MVVM
To Avoid Glue Code

8. RULES OF MVVM COMPLIANT
APPLICATIONS
• Minimum Code Behind (Recommended No code Behind)
• Events as Commands
• ViewModel as DataContext
• Design View and ViewModel Independently

9. INOTIFYPROPERTYCHANGED
• any class that implements this interface, notifies any listeners
when a property has changed.
• Notifies clients that a property value has changed.
• To implement INotifyPropertyChanged you need to declare
the PropertyChanged event and create
the OnPropertyChanged method. Then for each property you
want change notifications for, you
call OnPropertyChanged whenever the property is updated.

10. ICOMMAND
• Methods
1.CanExecute (Defines the method that determines whether the
command can execute in its current state.)
2.Execute(Defines the method to be called when the command
is invoked.)
• Events
1.CanExecuteChanged (Occurs when changes occur that affect
whether or not the command should execute.)

11. OBSERVABLECOLLECTION
An ObservableCollection is a dynamic collection of objects of a given type.
When an object is added to or removed from an observable collection, the UI
is automatically updated.
WPF automatically adds a CollectionChanged event handler to the
ObservableCollecion's events.
public class ObservableCollection<T> : Collection<T>,
INotifyCollectionChanged, INotifyPropertyChanged

12. PROS & CONS
• Cons
Ease of Maintainance
Ease of Testing
Flexibility
Re Usability
Low Degree of coupling
• Pros
Not Suitable for Simple Applications (Need best coding practices and standards)
Not a standardized one , Everyone follows their own flavours

13. PRACTICAL IMPLEMENTATION

14. SUPPORTED FRAMEWORKS AND
REFERENCES
• WPF Team : MVVM Toolkit
• MS Pattern and Practice Team : Composite WPF (Prism)
• Josh Smith. "MVVM Foundation"
• Sacha Barber. "Cinch."
• Karl Shifflett. "Ocean"
• Laurent Bugnion. "MVVM Light Toolkit"
• Lester Lobo. "CoreMVVM"
• Rob Eisenberg. "Caliburn"
• William e Kempf. "Onyx"
• Peter O’Hanlon. "GoldLight"
• jbe. "WPF Application Framework (WAF)"
• Paul Stovel : MacroModels
References:
http://www.codeproject.com/Articles/659614/MVVM-in-Depth
http://www.codeproject.com/Articles/165368/WPF-MVVM-Quick-Start-Tutorial (For Practical
Implementation)