Patterns For The Rest Of UsName: David HillTitle: Principal ArchitectCompany: Microsoft Patterns & PracticesSession Code: ARC303

Who Is This Talk For?

Patterns For The Rest Of Us…This talk is for you if:

You build real-world applicationsYou know your chosen language very wellYou know your way around the .NET FrameworkBut...

You find your applications are hard to maintain, extend or upgradeYou find it difficult to explain how your application is designed or structuredYou find yourself spending time on plumbing instead of business functionality

What Are Design Patterns?

Proven solution to common problems, challenges or requirementsThink of them as a template or recipe to help you design and structure your applicationSome Real-World Examples:

Patterns For The Rest Of Us…What Are Design Patterns?

Why Use Design Patterns?

Patterns For The Rest Of Us…Why Use Design Patterns?

Increase QualityEncapsulate best practices

Increase UnderstandingProvide common vocabularyMake it easier to read, communicate, document

Increase MaintainabilityMake it easier to fix, extend or upgrade

Increase ProductivityLess time on plumbing code, more time on application specific code

Patterns For The Rest Of Us…Why Use Design Patterns?

Increase TestabilityMake it easier to automate testing of your application

Increase FlexibilityMake it easier to add new functionality or customized behavior

Support Modern Development TechniquesAgile, Test-Driven-Development, Unit Testing

A bit of a no-brainer huh?

Where Did They Come Frome?

Patterns For The Rest Of Us…A Brief History Of Patterns #1

First There Was Object-Orient-DesignEncapsulation, Polymorphism, Inheritance!Object-Orient-Modeling & Visualization Tools!Woo Hoo!!!

But, If You’re Not Very Careful:

Patterns For The Rest Of Us…The Life Cycle of Bad Source Code

Complex Interactions Between ClassesReferences, Pointers, Multiple Base Classes, Virtual Methods, Macros, Templates, Operator Overloading

Leads To Complicated CodeCode that is hard to read & followCode that is fragile & hard to extendCode that is ‘styled’ – Macros vs Templates!Code that is hard to documentOriginal authors tend to disappear… and with it understanding of the design

The Gang of Four (GoF)Fathers of the design pattern movementFormalized and Categorized Common Patterns:

Creation PatternsHow, Where, When, Why do you instantiate objects?GOF: Factories, Builder, Prototype, Singleton

Structural PatternsChange, Migrate, Add to, Copy, Split, Move objectsGOF: Adapter, Bridge, Composite, Decorator, Façade, Flyweight, Proxy

Behavioral PatternsPassing around, working on, alter, add functionality to objectsCommand, Chain of Responsibility, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template, Visitor

Patterns For The Rest Of Us…Enter The Gang Of Four!

Patterns For The Rest Of Us…A Brief History Of Patterns #2

Them Came Component Oriented DesignHigher level abstractions for object interactions – Properties, methods, events, interfacesComponent infrastructure – discovery, creation, design-time and run-time pluggabilityGreatly simplified by Java & .NET!!

So What Changed?

Simpler Interactions Between ComponentsImproved Re-Use OpportunitiesThird Party Components & Building BlocksPluggable Architectures

How Did Patterns Evolve?

Patterns For The Rest Of Us…A Brief History Of Patterns #2

Enough Talk. Show Me The Code!

Observer Patterns

demo

Singleton Patterns

demo

Factory Patterns

demo

Command Patterns

demo

Template Patterns

demo

And Finally…

Anti-PatternsSquare Pegs / Round Holes

Don’t use a pattern just becauseDon’t be afraid to adapt a pattern to suit your needsDon’t over engineer your code to use a patternDon’t make fun of others & Don’t be dogmaticDon’t overuse a pattern

If every class uses the same patternit’s probably over usedThis is an easy trap to fall into.

Recommended ReadingWhere To Learn More

Elements of Reusable Object-Oriented SoftwareCommonly known as “The Gang of Four”

Martin Fowler’s PoEAAPatterns of Enterprise Application Architecture

O’Reilly: Head First Design PatternsJoshua Kerievsky

Refactoring to PatternsDoFactory.com

What Previous Attendees Have Said..."Overall, conference was great, gave us good roadmap to follow.""Thank you for all the great ideas. I am looking forward to going home and applying them.""Many of the things I learned here will revolutionize our practices, processes, designs, and patterns. THANKS!""Speakers were great“"Excellent conference, just first day alone was worth the money. Thank you.""This was an excellent value and I would recommend it to everyone!!""All speakers were very knowledgeable and they addressed many issues that I face every day.""This was an excellent conference for me. I'm taking away some useful tools.“

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Special ThanksBrainstorming, Session Guidance & Inspiration

Scott Cate(!)Jeffrey PalermoGlenn BlockWard BellJames AveryPaul GlavichJeff Widmer

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© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,

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