this deck (and sample code) was used for several presentations of this talk: nh code camp...
TRANSCRIPT
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?