Mvvm pattern

MVVM Pattern

MahenderSenior Software Engineer

United Health Group

Mahender Sarangam• Having 5 years of experience on .NET Technologies.

Working as a Senior Software Engineer in United Health Group (UHG India Information Service Ltd.). Worked with Big Firms like Deloitte Consulting & Wipro Technology.

• Got Technical Acquaintance on Technologies like C#, ASP.NET,AJAX, LINQ, Silverlight, WPF,WCF ,SQL Server, Team Foundation Server(TFS) and SharePoint Technology.

• MCTS Certified in Web Technologies.• Blog : http://Msarangam.wordpress.com

Why Do need PatternEverything in code behind, is not a good idea

Why Do need Pattern• Basic Motivation of separation pattern

– Removing logic from Code behind– Interchanging UI screens– Create Unit test case foe logic and UI– Developers and Designers can work parallel.– Model never needs to be changed to support changes to the

view– No duplicated code to update views

• So what is MVVM ?– Its variation of MVC pattern– John Gossman from WPF team – Resources from external assemblies– Martin Fowler's Presentation Model (PM) pattern

MVC & MVP Difference

Diagram• View Knows VIEW MODEL• VIEW MODEL Knows MODEL• BUT VIEWMODEL does not know View

View View Model Model

View• Represents the user interface that the

user will see.• Can be a user control or Data Template• Keep the view as simple as possible.• Uses Binding to “subscribe” to the

ViewModel• Interprets business data and state of

ViewModel to the human• Nothing but Presentation - XAML• No or minimal code-behind

View Model• An abstraction of View• Connector between View and Model• Keep View State, Value Conversion• No strong or weak (via Interface) reference of

View• Make VM as testable as possible (e.g. no call to

Singleton class)• No Control related Stuff in VM• Provides data to and from the View• Responds to both the View and the Model• Informs the View of changes in the data• Reusable (at least much more than code behind

a form)

Model• Can be Data Model, DTO, POCO,

auto-generated proxy of domain class and UI Model based on how you want to have the separation between Domain Service and Presentation Layer

• No reference to View Model• Typical class that covers a database• Could be a WCF Service and its client

reference

Supporting Libraires and Framework

• 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

Thank you