1. Portable Class Library: Tomorrow's Apps Today
Jeremy Likness (@JeremyLikness)
Principal Consultant
jlikness@wintellect.com
Copyright © 2012
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2. what we do
consulting training design debugging
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3. Building Windows 8 Apps with C#
• http://bit.ly/win8design
• Free source at:
http://windows8applications.codeplex.com/
• Everything you need to build and
deploy Windows Store apps
using C# and XAML
• Includes the portable project you
will see today
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4. Agenda
• Introduction to the Portable Class Library
• Understanding Extension SDKs
• Portable profiles
• Chasing ICommand: PCL Under the Hood
• Porting existing code
• Strategies for building new applications
• Comprehensive Example: Wintellog
• PCL Futures
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5. Introducing PCL
• Write and build managed assemblies that work (without
recompiling) on more than one .NET Framework platform
• Target frameworks include:
– .NET Framework 4 and later (including WPF)
– .NET for Windows Store apps (Windows 8)
– Silverlight 4 and later
– Windows Phone 7 and later
– Xbox 360
• Eliminate sharing of source
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6. Supported Features
Feature .NET Windows Silverlight Windows Xbox 360
Framework Store Phone
Core Yes Yes Yes Yes Yes
XLINQ 4.0.3+ Yes Yes Yes Yes
LINQ Yes Yes Yes Yes
Network Yes Yes Yes Yes
Serialization Yes Yes Yes Yes
WCF Yes Yes Yes Yes
IQueryable Yes Yes Yes 7.5+
MVVM 4.5 Yes Yes Yes
MEF Yes Yes Yes
Numerics Yes Yes Yes
Dynamic 4.5 Yes Yes
Annotations 4.0.3+ Yes Yes
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7. PCL in MSDN Documentation
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8. PCL in MSDN Documentation
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9. PCL and Model-View-ViewModel
• .NET Framework 4.5, .NET for Windows Store apps,
Silverlight, and Windows Phone
• Observable collections (normal and read-only)
• Notify property changed
• Notify collection changed
• Notify data error info
• ICommand
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10. PCL + VS 2012 = Extension SDK
• Software Development Kit (SDK) is a collection of files that Visual
Studio will treat as a single item
– Platform SDK – mandatory for a target platform, i.e. "Windows 8 SDK"
– Extension SDK – optional components to extend a platform
• Target Platform Moniker (TPM) = Identifier (TPI) and Version (TPV) ex:
"Windows, version=8.0"
• References (binaries, either .WinMD or
assemblies), redistributables, and design-time components
• Can drop any components to a path with a TPM and Visual Studio will
substitute that path
• Easy to see what the target profile is
• Each combination of target platforms creates a unique profile
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11. PCL Under the Covers
• Use ILDASM to inspect portable assemblies
• ICommand lives in System.Windows.dll for Silverlight, but System.dll in .NET
4.5 and Windows.UI.Xaml.Input.dll in Windows Store apps ("retargetable")
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12. PCL Under the Covers (cont.)
• Classic type forwarders route to the appropriate assembly
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13. PCL Under the Covers (cont.)
• Windows Store apps forward to System.ObjectModel and language
projections maps them to the WinRT framework
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14. demo
Basic MVVM with PCL
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15. Porting Existing Code
• Always easier when implementing MVVM, but are your
ViewModels tied to views (i.e. do you include XAML
namespaces?)
• Decoupled code is key
• Identify key APIs that are platform-specific and implement
façade
• Common areas to refactor out include UI, networking, and
storage
• Convert an existing class library to a PCL assembly
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16. Porting Existing Code
• You can convert an existing class library to a PCL
• First, unload the project
• Second, change the settings:
<Import Project="$(MSBuildToolsPath)Microsoft.CSharp.targets"
/> to
<Import
Project="$(MSBuildExtensionsPath32)MicrosoftPortable$(Target
FrameworkVersion)Microsoft.Portable.CSharp.targets" />
• Next, add the following project GUIDs to the end of the first property
group – this adds the library tab and dialog to change the targets:
<ProjectTypeGuids>{786C830F-07A1-408B-BD7F-
6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-
00C04F79EFBC}</ProjectTypeGuids>
• Finally, reload the project and select the target frameworks
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17. Strategies for Building New Apps
• Follow S.O.L.I.D. Principles – they do make it easier
– Single responsibility – a class should only do one thing and change for one reason
– Open/closed principle – open for extension, closed for modification
– Liskov substitution principle – no side effects/unexpected behaviors when cast to a base class
– Interface segregation – interfaces should be focused on specific, targeted functionality
– Dependency Injection – keep dependencies external from your class and inject them
• Use MVVM and keep view-specific code in the view, not the view model
• Target the smallest number of frameworks possible in your portable
assemblies to ensure the widest surface area of APIs to choose from, i.e. don't
include Xbox if you're not going to write for it
• Pick a target platform to run your unit tests and only write tests for PCL
assemblies in that target
• Don't forget to write unit tests for the classes that are specific to target
platforms
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18. demo
Wintellog: Windows Store and WPF
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19. Recap
• PCL is native to VS 2012 and uses Extension SDKs
• PCL maps target frameworks to profiles that represent a
"lowest common denominator" of API surface area
• Under the hood, PCL takes advantage of type forwarders
and Windows 8 advances to enable the portable assembly
• Existing code can be ported to use the PCL
• New applications should take advantage of the PCL for
various core assemblies, with storage and UI abstracted
away
• PCL should be a solid investment as the team is actively
working on updates to keep pace with the latest
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20. Questions?
Jeremy Likness (@JeremyLikness)
Principal Consultant
jlikness@wintellect.com
consulting training design debugging wintellect.com