1. 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!

2. New England Code Camp #13 27-March-2010
Demystifying Prism
Building Silverlight and WPF applications using
Composite Applications Guidance (CAG) and
Composite Application Library (CAL)
New England Code Camp #13
27-March-2010
Not representing my day job
Boston Azure User Group
@bostonazure
Bill Wilder
@codingoutloud
Boston West Toastmasters
Not here with my day job Only Bill’s personal views
Copyright (c) 2010, Bill Wilder

3. 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 assumptions about your background
Unit Testing, DI, IoC, SoC
Code-Behinds
Ask questions any time
image from

4. 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

5. Assumptions: You have heard of…
WPF (Windows Presentation Foundation), Silverlight, XAML
Unit Testing (nUnit, …), TDD
Dependency Injection (DI), Inversion of Control (IoC), Loose coupling
UI Design Patterns (MVVM, MVC, MVP, …)
Where are YOU coming from?

6. Terminology Prism  code name (which I will call it)
Photo from
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”
And can test w/o Presentation code

7. Okay, so this stuff ain’t easy
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 this stuff ain’t easy

8. Industry Response

9. Where did Prism come from?
P&P =
Patterns & Practices Group
microsoft.com/patterns

10. 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
Products: Windows, Office, Exchange, Visual Studio, .NET, Zune, ...
P&P Group
Backward compatibility
Maturity
Lessons from CAB = Composite UI Application Block
Learned Composite = Goodness
Prism, Prism v2:
Easier to adopt incrementally
Less invasive
Products: EntLib, CAB, Unity, Prism v1, Prism v2, Arch Guide, …

11. Prism Key Concepts Eye Chart
[Source CAL docs]

12. Stock module
- send an TickerSymbolSelectedEvent to the EventAggregator
Other modules
- request to subscribe to TickerSymbolSelectedEvent

13. REPLAC NEXT SLIDE WITH VISUUALLS
Todo

14. Shell = Main Window

15. Examine Demo Stock Trader RI (RI = Reference Implementation)
Code
Examine Demo Stock Trader RI
(RI = Reference Implementation)

16. 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

17. <TextBox Text="{Binding Path=TextContents}" FontSize="36" />
Classs FredViewModel
public string TextContents { get; set; }

18. 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

19. 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

20. 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

21. Events .NET events WPF events Composite events (Prism)
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
Subscriber and Publisher lifetimes not bound
More: Force to UI thread; event filtering

22. 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

23. Prism is (relatively) Small
Silverlight

24. 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)

25. Build Prism app that has a multiple modules and views
Code
Build Prism app that has a multiple modules and views

26. 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)

27. Examine and Extend Hello World
Code
Examine and Extend Hello World

28. 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
Prism docs refer to as Presentation Model
I will refer to as ViewModel pattern

29. Code-Behind Pattern (Old Way)
Load external data from web services, etc.
Supported by WPF / SL
View
Model
Your Other Glue
Code Behind for each Control
Commanding also spans View & ViewModel
No UI in VM
MVP is a delegation model – MVVM handles this with data binding – way less code in the code-behind
Silverlight controls don’t automatically implement ICommand
UI “is” the data store for much of the data (e.g., ListBox); logic intertwined
Custom code to populate UI

30. ViewModel Pattern (New Way)
Load external data from web services, etc. (“usual stuff”)
Supported by WPF / SL
View
ViewModel
Model
Data Binding
Your Glue
Commanding also spans View & ViewModel
No UI in VM
MVP is a delegation model – MVVM handles this with data binding – way less code in the code-behind
Silverlight controls don’t automatically implement ICommand
Powerful Data Binding glue provided free with both Silverlight and WPF
Custom code (boring); Automapper is promising

31. Modify Prism app UI to use M-V-VM
Code
Modify Prism app UI to use M-V-VM

32. DataContext & {Data Binding}
xmlns:models=“clr-namespace:MyClrClass. Models” …
<Window.DataContext> <models:EditViewModel/> …
Enables

33. Prism Rough Edges Coming in fall: Prism 4
MEF alignment
Prism templates, tooling
We do have Project Linker, David Hill’s templates
You build it; P&P does not ship a binary
Hopeful for Prism 4
Cannot unload a Module from memory
Debugging: when a composite event fires and nobody is listening, how can I tell?

34. When should you use Prism?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

35. Wrong reason to choose Prism

36. 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]

37. 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]

38. 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]

39. 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!

40. Official Site http://microsoft.com/compositewpf
-- or --

41. Futures

42. Watch these spaces
“Contrib”
Assorted contributions for Prism (currently v1)
Channel 9 for tutorial videos
Infragistics control adapters for
Region Adaptors for Prism (currently v1)

43. Prism v2 References 

44. Other Resources
Josh Smith on MVVM with WPF:
Brian Noyes on Understanding Routed Events and Routed Commands in WPF:
WPF Commanding Overview:
Martin Fowler’s description of Presentation Model pattern:
XAML Guidelines for Creating a Composite UI:

45. David Hill’s QuickStart Kit (new, raw): http://blogs. msdn
David Hill’s updated QuickStart Kik (I have not had chance to look at it – was just posted):

46. Silverlight FCL/XAML != WPF FCL/XAML

47. Did I get to this?
What would happen if I ran the Synchronous retrieval of the Podcast feed from Silverlight?
Show the Prism docs

48. 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, security, useful, choose 1, async, cross-domain)
Challenge #3: Silverlight XAML != WPF XAML
But is converging on mostly a subset
Other miscellaneous differences…
Suggestion: Write 1st in Silverlight, then port to WPF
Jon Pelak’s slide?

49. Questions?

50. 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

51. 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; }
Answer:
Prism runtime calls CreateShell.
The call to Container.Resolve invokes the Unity DI (Dependency Injection) container which knows it needs to create a ShellView object.
Unity notices that the ShellView constructor requires a ShellViewModel object and creates one so that it can pass it in.

52. 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>();
Answer:
Prism runtime calls CreateShell.
The call to Container.Resolve invokes the Unity DI (Dependency Injection) container which knows it needs to create a ShellView object.
Unity notices that the ShellView constructor requires a ShellViewModel object and creates one so that it can pass it in.

53. View, ViewModel, or Model?
public class Foo : INotifyPropertyChanged {
// My most likely role is…? }

54. Loose Coupling – How To
Architect for general flexibility using Dependency Inversion & code to interfaces
Use an IoC container (Unity, Structure Map, Castle Windsor, Ninject, …)
Unit test using IoC

55. not all-or-nothing prospect
- more guidance than doctrine, e.g., startup
- need container, don't need everything in the bootstrapper b/c you won't need
don't need container for just loosely coupled events usage, for example
STD APP:
- module loading
- view injection
MODULAR LOADING
- are they cached after loading?
- complements Transparent Platform Extensions
NOVIGATION FRAMEWORK
- orthogonal; see blog post

56. Prism-izing a Silverlight App
Create new Silverlight App
Add References
Microsoft.Practices.Composite.dll
Microsoft.Practices.Composite.Presentation.dll
Microsoft.Practices.Composite.UnityExtensions.dll
Microsoft.Practices.ServiceLocation.dll (?)
Microsoft.Practices.Unity.dll
Add Bootstrapper : UnityBootstrapper
Invoke from Application_Startup
Create Shell
Add View (UserControl)
Define Region
Add Module (IModule)
Inject View
Add Command
Unlike CAB – does not totally take over your app-dev experience

57. ICommand
Loosely-coupled goodness to connect UI gesture to resultant action’s logic
WPF supports ICommand, limited to Visual Tree
ICommand exists only as a place-holder in Silverlight
Prism implements ICommand without limiting to Visual Tree
Better than the default WPF experience
Why is this important?

58. Rename MainPage => Shell
Refactor tool

59. Transparent Platform Extensions vs. Prism Remote Module Loading
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

60. 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

61. 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

62. Next Steps Download Prism Look at the samples, read the docs
Download David Hill’s updated QuickStart Kit from

63. Where to put “Are you sure you want to close without saving?” code?