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

1. 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)

2. 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) Prism is 100% Resume Compliant!

3. Introduction to Prism Building Silverlight and WPF apps with Composite Applications Guidance and Composite Application Library Bill Wilder http://blog.codingoutloud.com

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… • 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?

6. 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

7. 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”

8. 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

9. IndustryResponse

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

11. 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 Windows, Office, Exchange, Visual Studio, .NET, Sharepoint, Zune, ... P&P Group • EntLib, Unity, Arch Guide • CAB, Prism v1, Prism v2

12. Demo Stock Trader RI (RI = Reference Implementation)

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

14. 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

15. 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)

16. 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]

17. 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

18. Prism is (relatively) Small Silverlight

19. First Cut At “SaveAsPodcast” App Look at some code…

20. 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)

21. 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

22. ViewModel Pattern Load external data from web services, etc. Supported by WPF / SL View ViewModel Model Data Binding Your Glue Powerful Data Binding glue provided free with both Silverlight and WPF Custom code (boring); Automapper is promising

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

24. Port “SaveAsPodcast” to Prism M-V-VM Modules Eventing Event Filtering

25. 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?)

26. 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]

27. 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]

28. 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]

29. Wrong reason to choose Prism

30. 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

31. Official Site http://microsoft.com/compositewpf -- or -- http://codeplex.com/compositewpf

32. 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)

33. Prism v2 References • http://www.microsoft.com/downloads/details.aspx?FamilyID=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

34. 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

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

36. 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, 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

37. Questions?