Presentation on what and how of MVVM design pattern usage in Windows Presentation Foundation.

1. M-V-VM
Model View ViewModel for WPF
(Design Pattern)

2. Highlights
Created By John Gossman (WPF and Silverlight
Architect at Microsoft)
This pattern is a simple and effective set of Guidelines
for Designing and Implementing a WPF application
Allows you to create a strong separation between
data, behavior and presentation (UI)

3. Uses
Databinding for 2 way communication between View
(UI) and ViewModel
Uses Command pattern (ICommand interface) for
communicating actions or events that happen on View
(UI)
Dependency Properties alongwith Data Binding to
communicate data changes to and from the View (UI)

4. WPF MVVM Application Layers

5. What is View, Model and ViewModel?
View ViewModel Model
• represents the UI that the end • is the abstraction of the View • Represents the data classes
user sees (UI) and contains the data, bound
• can be a user control or Data • Communicates data to view and modified by view
Template modifications to the Model • Hold only the data or
• shouldn’t contain any logic or from the View information related to an
code that is to be tested • Data changes in Model are Object;
reflected in the View through • It doesn’t contain the
ViewModel by making use of behaviors or services that
data Binding and dependency manipulate this data or
properties information, though
sometimes it may contain data View knows
validation logic Multiple Views : 1
ViewModel, ViewModel
• Example is “The Contact 1 View : 1 ViewModel ViewModel (for Wizard
information of a person” like knows Model, but not
kind of applications)
Name, Phone vice versa
No, Email, Address, Zip Code
etc.

6. Advantages
ViewModel classes are easy to unit test the complete UI without touching the UI code
Testing through ViewModel provides free and fast regression testing which helps to
reduce cost of maintaining application over time
Helps create a smooth Designer/developer workflow
• Design team can focus on creating user-friendly views while,
• Development team can focus on creating robust ViewModel classes
• Which can then be integrated to ensure proper data bindings exist in the View’s XAML file
Takes full advantage of WPF’s Data Templates and Commands
Gives more flexibility to change UI without having to refactor the logic or change other
code base

7. What do u need to Understand in
Order to Learn and Implement MVVM
Data Binding in WPF
• http://msdn.microsoft.com/magazine/cc700358
Command Pattern Implementation in WPF
• ICommand Interface usage
public interface Icommand
{
bool CanExecute(object param);
void Execute(object param);
event EventHandler CanExecuteChanged;
}
• RelayCommand pattern
• Routed Events and Commands in WPF
• http://msdn.microsoft.com/magazine/cc785480
Composite Application Library from Microsoft
• http://msdn.microsoft.com/library/cc707890
For Unit Testing:
• Nunit
• Moq Framework for .Net (Third Party classes for testing .Net Apps)

8. References and Resources
WPF Model-View-ViewModel Toolkit
•http://wpf.codeplex.com/wikipage?title=WPF%20Model-View-ViewModel%20Toolkit
MVVM Foundation on codeplex (A set of classes that helps build WPF Apps based on MVVM)
•http://mvvmfoundation.codeplex.com/
Super Simple MVVM Explained video:
•http://www.charlieblog.net/SuperSimpleMVVM/Large/SuperSimple_MVVM_large/SuperSimple_MVVM_large.html
MVVM MSDN Article:
•http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
MVVM Channel9 video with Karl Shifflett
•http://channel9.msdn.com/shows/Continuum/MVVM/
WPF MVVM Video by Jason Dolinger
•http://hugeonion.com/2009/03/08/wpf-mvvm-video-by-jason-dolinger/
MVVM Explained
•http://csharperimage.jeremylikness.com/2010/04/model-view-viewmodel-mvvm-explained.html

9. Last Note on MVVM
• It is said that if you have not given names for
your UI Elements and still able to run and
process the application properly, the MVVM
Implementation is clean, complete and proper
– THANKS