Prism is 100% Resume Compliant!• Trendy design patterns!• Test-Driven Development• Loosely Coupled• Blend-able UIs• Interface-based

Programming• Dependency Injection (DI)• IoC Containers• Be a Code-Behind snob!• Already know EF, MVC,

WPF, (W)WF, WCF, and WTF? Add Prism to the list!

• Separate concerns with ease and style

• Write S.O.L.I.D. Code

• Modular, Composite Apps!• Distributed Agile Teams• Twice as much code in

double the time!• Fluent Interfaces• Multi-Targeting to

Silverlight and WPF• Routed Commands &

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

Demystifying Prism

Bill Wilder

http://blog.codingoutloud.com

Building Silverlight [and WPF apps] withComposite Applications Guidance and

Composite Application Library

New Hampshire .NET User Group17-June-2009

image from http://en.wikipedia.org/wiki/Rubik%27s_cube

Creative Commons License

This slide deck is © Bill Wilder 2009 and licensed under the Creative Commons Attribution (BY) + Share Alike (SA) license:

http://creativecommons.org/licenses/by-sa/3.0/

Excluding the slide/page with the frame from a Dilbert cartoon.

How to Demystify Prism?• How did we get here? (motivation)• Demonstrate a few key Prism concepts• Focus on Prism, not (for example):

– XAML, Silverlight, WPF– M-V-VM Pattern

• Making assumptionsabout your background– Unit Testing, DI, IoC, SoC– Code-Behinds

Ask questions any time

image from http://en.wikipedia.org/wiki/Rubik%27s_cube

Terminology

• Prism code name (which I will call it)• Prism 2.0 2nd release (Feb 2009)• 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”

Photo from http://en.wikipedia.org/wiki/File:Dispersion_prism.jpg

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

Products: EntLib, CAB, Unity, Prism v1, Prism v2, Arch Guide, …

Products: Windows, Office, Exchange, Visual Studio, .NET, Zune, ...

Demo Stock Trader RI

(RI = Reference Implementation)

What can Prism do for You?

Manage complexity via loosely-coupled design & clean Separation of Concerns at many levels

• Composite UI (Regions) & Modules– Supports independent development and evolution

• Loosely coupled Eventing and Commanding– Enhances support for M-V-VM Design Pattern

• Design guidance and patterns that support both Unit Testing and Designer Integration

• Excellent support for SL/WPF portability

The Case for Prism: “Silverlight++”• SoC + SRP + reducing plumbing code + Unit Tests

best way to handle complexity and enable ability to respond rapidly to requirement changes

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

• Prism best way to support the previous item (in SL/WPF)

• Prism is an exemplar of modern-day best practices for the Silverlight and WPF platform

• Prism sits atop full power of SL/WPF, and fully leverages Unity and .NET, enables Agile

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 live in Modules

• Modules are DLLs (Visual Studio Projects)– Nice unit of work for a sub-team, testable

• Shell decides when/whether to load Modules– Configured via code, XML file (WPF only), or XAML

• Modules can be downloaded (over http)– Silverlight, WPF Click-Once can streamline startup– Can write your own loader rules

• For its UI, a (Prism) Module loads its (Prism) View

Events

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

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

• Composite events (Prism)– 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 (MVP good too)

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

Prism is (relatively) Small

WPF

Prism

Silverlight

Create an App Together

• Using (very early) Shell template from David Hill (download instructions later in this deck)

• Add Prism references, Discussion Shell, Bootstrapper, Regions

• Add Prism Module, new View, register View with RegionManager, add to Module Catalog

• Implement M-V-VM• Show loose coupling and modular design• Wash, rinse, repeat (evolve the design)

CodeCodeBuild Prism app that has a multiple

modules and views

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

– Dev in Visual Studio, Designer in Expression Blend– Iterate from “Dev Ugly” to crafted UI

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

• Better organized code is better code– Easier to understand, maintain, reuse (time & space)

– 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

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.

ViewModel Pattern (New Way)

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. (“usual stuff”)

CodeCodeModify Prism app UI to use M-V-VM

Prism Rough Edges

• Not yet updated for Silverlight 3– Possibly not optimized– Nav Framework, Transparent Platform Updates

• You build it; P&P does not ship a binary• No Prism-specific templates*, tooling* for Visual

Studio (poor cousin to ASP.NET MVC)*We do have Project Linker, David Hill’s templates

• Cannot unload a Module from memory• MEF alignment

When should you use Prism?

? ? ? ? ?? ? ? ?? ? ? ?? ? ? ?? ? ? ?? ? ? ?? ? ? ??

Wrong re

ason to

choose Prism

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]

Prism is not all-or-nothing

• Can use Eventing, Commanding support without Composite Applications– Better M-V-VM than possible with SL or WPF alone

• Prism’s Project Linker tool eases sharing code across Silverlight and WPF

• Prism’s design goals aligned with features in Silverlight and WPF– Expand your thinking beyond WinForms, WebForms

• Read the docs and guidance!

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

• David Hill’s QuickStart Kit (new, raw): http://blogs.msdn.com/dphill/archive/2009/05/29/prism-quick-start-kit.aspx

• David Hill’s updated QuickStart Kik (I have not had chance to look at it – was just posted): http://blogs.msdn.com/dphill/archive/2009/06/15/prism-quick-start-kit-update.aspx

Silverlight FCL/XAML != WPF FCL/XAML

• http://wpfslguidance.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=28278

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 desktop– But it is source compatible (but see #2)

• Challenge #2: runtime subset 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: Silverlight XAML != WPF XAML– But is converging on mostly a subset

• Other miscellaneous differences…– http://wpfslguidance.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=28278

• Suggestion: Write 1st in Silverlight, then port to WPF

Questions?

Name some major Prism concepts

• Bootstrapper (a convention)• Shell (“main window”)• Region• View• Module• Service (talk to outside world, web service)• Event (loosely coupled, cross module)• Command

How does the View get created?public partial class Bootstrapper : UnityBootstrapper {…protected override DependencyObject CreateShell(){ // Container.Resolve is part of Unity ShellView view = Container.Resolve<ShellView>();

Application.Current.RootVisual = view; return view;}…

How does View get its ViewModel?

• Bootstrapper.cs:FooView view = Container.Resolve<FooView>();• FooView.cs:public ShellView(FooViewModel viewModel) { … }• FooModule.cs (in IModule:Initialize): container.RegisterType<IFooViewModel,

FooService>();

View, ViewModel, or Model?

public class Foo : INotifyPropertyChanged

{ // My most likely role is…?}

Transparent Platform Extensionsvs.

Prism Remote Module LoadingTransparent Platform Extensions• New in Silverlight 3• Supports caching of new platform features (browser does the

caching)• DLR, Language Extension, Controls• Do not need to live in XAP• Specified in AppManifest.xaml• Only can be downloaded from microsoft.com

Prism Remote Module Loading• Modules for your application, not Platform• Defer loading for UX reasons, future modularity flexibility

What is a “View”

• Prism uses the term to mean a visual area, hosted in a module, that is displayed within a (Prism-defined) Region

• M-V-VM uses the term to mean the implementation of your UI dealing with drawing the screen (but does not include logic)

• Don’t confuse the two

What is a “Service”

• Prism uses the term to refer to modules which supply data and logical processing to Views in a loosely coupled manner

• The SOA world uses the term to refer to (usually) application-independent business components which can be invoked over a network using a standard protocol, usually SOAP or REST-based; often implemented as “Web services” using ASMX or WCF in .NET

Next Steps

• Download Prism• Look at the samples, read the docs• Download David Hill’s updated QuickStart Kit

from http://blogs.msdn.com/dphill/archive/2009/06/15/prism-quick-start-kit-update.aspx