This deck (and sample code) was used for several presentations of this talk:

• NH Code Camp (28-Feb-2009)• Beantown .NET User Group (05-Mar-2009)• Boston Code Camp 11 (28-Mar-2009)

Prism is 100% Resume Compliant!• Fancy design patterns like

Model-View-ViewModel• Test-Driven Development

(TDD)• Loosely Coupled• Separation of Concerns

(SoC)• Interface-based

Programming• Dependency Injection (DI)• Inversion of Control (IoC)

Containers• Code-Behind minimalist

• Modular, Composite Application

• Distributed Agile Team• Reverses baldness• Fluent Interfaces• Multi-Targeting Silverlight

and WPF• Routed Commands &

Routed Events• High Performance Dev• Increases your IQ 42 points• Data Binding• Architect (not Astronaut)

Introduction to Prism

Bill Wilder

http://blog.codingoutloud.com

Building Silverlight and WPF apps withComposite Applications Guidance and

Composite Application Library

What is this talk about?

• Targeting Silverlight and/or WPF– Managing complexity well– Best practices for Testability and design

patterns

• Focus (mostly) around UI concerns– XAML, Code-behinds, Data Binding

• Doing all of the above Using Prism– Runtime Library + Guidance + Project Linker

Assumptions: You have heard of…

• Windows Presentation Foundation (WPF), Silverlight, XAML

• Unit Testing (nUnit, …), TDD• Dependency Injection (DI), Inversion of

Control (IoC), Loose coupling• UI Design Patterns (MVC, MVP, …)

Where are YOU coming from?

Goals of this Talk

• Appreciate value of Prism for SL and WPF• Demonstrate a few key Prism concepts

Side effects:• A little WPF, Silverlight; discuss a couple of

Design Patterns / Anti-Patterns

Rules of engagement:• Ask questions any time

Terminology

• Prism code name (which I will call it)• Prism v2 talking about 2nd release• Composite Application Guidance for WPF

and Silverlight official name of whole package

• Composite Application Library for WPF and Silverlight runtime support included – sometimes called “CAL”

What’s the problem?• US businesses annually spend ~ $250 billion on

software dev across approx 175,000 projects• Only 16 percent of these projects finish on schedule

and within budget• Another 31 percent are cancelled, mainly due to

quality problems• Another 53 percent exceed their budgets by an

average of 189 percent• Projects reaching completion deliver an average of

only 42 percent of the originally planned features

[Credit: Jack Greenfield, Microsoft]

Okay, so th

is stuff

ain’t easy

IndustryResponse

Where did Prism come from?

P&P = Patterns & Practices Group

microsoft.com/patterns

Product Groups • Long cycle times• Strategic• Very large teams• Cost money• Fully Supported

• Rapid cycle times• Small, focused agile teams

– Partner with community• Ship tactical solutions now

– Code and Guidance• Free, Open Source• More latitude, less legacy

P&P Group

• EntLib, Unity, Arch Guide• CAB, Prism v1, Prism v2

Windows, Office, Exchange, Visual Studio, .NET, Sharepoint, Zune, ...

Demo Stock Trader RI

(RI = Reference Implementation)

Prism Key Concepts Eye Chart

[Source CAL docs]

Shell, Regions, Views

• Shell is main window for app• Shell defines (visual) Regions• Regions control where UI will appear – flexible• Views are displayed within Regions

• WPF/Silverlight design, code, tooling still applies – Prism just makes it better

Views and Modules

• Modules are DLLs (Projects)– Nice unit of work

• You can decide when/whether to load• Modules can be configured to load code, XML,

or XAML• Modules can be downloaded (over http)

– Can write your own loader rules

• Modules have Views (usually)

Events

• .NET events– Tight coupling (references in both directions)

• WPF events– Looser coupling, (generally) limited to same visual tree

• Composite events– Looserer coupling; not limited to same visual tree

• More: Force to UI thread; event filtering• [Related to Commanding]

Prism “Conventions+”

• Bootstrapper• Shell• One module per DLL• M-V-VM pattern

• Don’t need to follow the conventions…• But you’ll be glad you did

Prism is (relatively) Small

WPF

Prism

Silverlight

First Cut At “SaveAsPodcast” App

Look at some code…

Why Separate Concerns in UI?• Optimizes Developer / Designer interaction

– Dev in Visual Studio, Designer in Expression Blend• Easier to Test

– Now possible to Unit Test (vs. Integration Test)– Simpler problem isolation

• Reuse opportunity goes way up– Same ViewModel can be reused with UI variations

• Better organized code is better code– Easier to understand, maintain– SE Principles: SoC, coupling, cohesion, SRP

(rendering, mouse & keyboard, disabled, hover)

How to Separate Concerns in UI?

• Use Code-Behinds reluctantly + M-V-VM• M-V-VM Model-View-ViewModel Pattern • Abbreviated as M-V-VM, MVVM• Often referred to simply as ViewModel• Specialization of Fowler’s Presentation Model

pattern where View knows about ViewModel– http://martinfowler.com/eaaDev/PresentationModel.html

• Prism docs refer to as Presentation Model• I will refer to as ViewModel pattern

ViewModel Pattern

View Data Binding ViewModel ModelYour Glue

Supported by WPF / SL

Powerful Data Binding glue provided free with both Silverlight and WPF

Custom code (boring); Automapper is promising

Load external data from web services, etc.

Supported by WPF / SL

Code-Behind Pattern (Old Way)

View ModelYour Other Glue

UI “is” the data store for much of the data (e.g., ListBox); logic intertwined

Custom code to populate UI

Code Behind for each Control

Load external data from web services, etc.

Port “SaveAsPodcast” to Prism

M-V-VMModulesEventing

Event Filtering

Prism Rough Edges

• You build it; P&P does not (yet) ship a binary• No Prism-specific templates for Visual Studio• Cannot unload a Module (MEF?)

When to go Composite? (1/2)

• You are designing “complex” WPF or Silverlight applications, or…

• You are building an application that presents information from multiple sources through an integrated user interface, or…

• You are developing, testing, and deploying modules independently of other modules, or…

[Source CAL docs]

When to go Composite? (2/2)

• Your app will add more views and more functionality over the coming years, or…

• You must be able to change the app quickly and safely to meet emergent business requirements, or…

• Your app is being developed by multiple collaborating teams; or…

• Your app targets both WPF and Silverlight, and you want to maximize code sharing between platforms.

[Source CAL docs]

When to NOT go Composite?

• Your apps do not require any of the above scenarios, or…

• Your application consists of a few simple screens, or…

• You are building a prototype or demo, or…• Your developers are not familiar with the

ideas and practices and do not have the time to learn them. * COMPLEMENTARY * (remember the opening slide)

[Source CAL docs]

Wrong re

ason to

choose Prism

Why Prism

• SoC + SRP + reducing plumbing code + Unit Tests best way to handle complexity and enable ability to respond rapidly to requirement changes

• M-V-VM best way to support the previous item (in SL/WPF)

• Prism best way to support the previous item

Official Site

http://microsoft.com/compositewpf -- or --

http://codeplex.com/compositewpf

Watch these spaces

• “Contrib” site @ http://compositewpfcontrib.codeplex.com/– Assorted contributions for Prism (currently v1)

• Channel 9 for tutorial videos– http://channel9.msdn.com/tags/Prism/

• Infragistics control adapters for Prism @ http://ncal.codeplex.com/– Region Adaptors for Prism (currently v1)

Prism v2 References• http://www.microsoft.com/downloads/details.aspx?Family

ID=fa07e1ce-ca3f-4b9b-a21b-e3fa10d013dd&DisplayLang=en

• http://blogs.msdn.com/jmeier/archive/2009/02/18/new-release-composite-application-guidance-for-wpf-and-silverlight-v2-0-prism.aspx

• http://timheuer.com/blog/archive/2009/02/18/prism-2-released-composite-guidance-for-silverlight-lob.aspx

• http://msdnrss.thecoderblogs.com/2009/02/18/composite-application-guidance-for-wpf-and-silverlight-v20-prism/

• http://tinyurl.com/d4s22b

Other Resources• Josh Smith on MVVM with WPF:

http://msdn.microsoft.com/en-us/magazine/dd419663.aspx

• Brian Noyes on Understanding Routed Events and Routed Commands in WPF: http://msdn.microsoft.com/en-us/magazine/cc785480.aspx

• WPF Commanding Overview: http://msdn.microsoft.com/en-us/library/ms752308.aspx

• Martin Fowler’s description of Presentation Model pattern: http://martinfowler.com/eaaDev/PresentationModel.html

• XAML Guidelines for Creating a Composite UI: http://msdn.microsoft.com/en-us/library/dd458877.aspx

Did I get to this?

• What would happen if I ran the Synchronous retrieval of the Podcast feed from Silverlight?

• Show the Prism docs

Silverlight for .NET• Challenge #1: not binary compatible with runtimes

that run on Windows desktop– But it is source compatible

• Challenge #2: only a subset of runtime is implemented on Silverlight– But most of the stuff that “makes sense” is there (subset, (subset,

security, useful, choose 1, async, cross-domain)security, useful, choose 1, async, cross-domain)

• Challenge #3: XAML not same as WPF– But is converging on mostly a subset

• Other miscellaneous differences…• Suggestion: Write 1st in Silverlight, then port to WPF

Questions?