This document discusses cross-platform development using C# and Xamarin. C# can be used to write code once that runs on Windows, iOS, Android, and other platforms using Mono and Xamarin. While HTML5 promises cross-platform capabilities, it requires JavaScript and does not provide full access to native platform features. C# allows access to native SDKs and most non-UI code can be shared across platforms. Xamarin tools enable developers to write fully native mobile applications in C# for iOS and Android.

1. Cross platform development
with C#
By Michele Scandura

2. Michele Scandura
Senior Software Developer at Compass Informatics (www.compass.ie)
EMAIL
michele.scandura@outlook.com
TWITTER
@mikescandy
BLOG
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3. But… HTML5?
“I think the biggest mistake that we made as a company is
betting too much on HTML5 as opposed to native”
(Mark Zuckerberg, Sept. 2012)
 HTML5 is indeed a great technology and is here to stay
 Promise: write once, run everywhere
 JavaScript engines are getting faster, and you can use JavaScript
on client and server
 But…

4. But… HTML5?
 You have to program in JavaScript 
 Write once, deploy everywhere not 100% true
 UI paradigms are different on each platform
 No access to native libraries

5. But… HTML5?
iOS Android Windows Phone

6. C# as a multiplatform alternative
 Plus a few nice additions
 Mono makes it possible to run
C# code on the most Playstation Mobile (PS VITA)
widespread platforms The Unity 3d Engine uses C# as a
All Windows variants scripting language (and Unity runs
on Wii and WiiU, PS3, XBOX, Flash)
Linux
PS4 will definitely run C# code
OSX
BSD, Solaris, Wii, PS3
iOS
CPU architecture is not an issue:
Android x86, x64, IA64, PowerPC, SPARC,
ARM…

7. Advantages in using C#
 Linq / Lamda, Parallel Linq, Tasks
 Memory management (no pointers, but leaks are still a problem)
 Strongly typed implicit variable declaration
 Extension methods
 Strongly typed
 Generics
 WCF
 Async/await
 (This applies only if using Visual Studio) ReSharper

8. C# as a multiplatform alternative
“Between Windows, iOS and Android, your C# code can
run on over 2.2 billion devices”
Nat Friedman (CEO of Xamarin, Jan 2013)

9. Introducing Xamarin
 Newly released tools: Xamarin Studio,
Xamarin.Android and Xamarin.iOS (formerly
Mono for Android and MonoTouch
 Provide full access to platform SDK
 100% native
 Faster than native! (Mono vs. Dalvik,
xobotos)
 Always in sync with native SDKs
 (iOS 6.1 released 28/1, MonoTouch update
released the next day)

10. Reusable code
 Most non-UI code can be shared across platforms
Core logic
Entities, messages, interfaces
Linq
Network access
 File / Database access might be tricky

11. Reusable code: how to
 File linking
 Abstraction
 Observer pattern
 Partial classes
 Conditional compilation
 Portable class libraries

12. Useful C# libraries
 TinyIoC / TinyMessenger
 WaveEngine
 MonoGame (XNA) We have IoC containers,
 EmguCv (open CV) MVVM, 2D and 3D game
 NetTopologySuite engines, ORM, Image
 MVVMCross processing library, Logging,
Web services, GIS tools…
 SQLite-Net
 ServiceStack
 Log4Net
 Many more

13. And native too
 Google Maps API V2
 Flurry
 OxyPlot.2DGraphLib
 Chipmunk Physics
 And many more

14. Tips and tricks
 Developing for iOS requires a Mac
 Emulators are good but:
 iOS provides an x86 simulator
 Android provides both ARM and x86 emulators
 iOS deployment still requires the usual certificates and some Xcode
 Memory leaks
 Git support in TFS / Xamarin Studio

15. Demo time (sort of!)

16. Conclusions
 It all sounds great, isn’t it?
 Sometimes is not straightforward as it seems
 Relying on semi-closed platform
 Specific platform knowledge is still a must: get ready to learn some
Java and objective-c
 Mobile is not only coding, UI and UX are crucial for a successful app

17. Some links
Apache Cordova - http://cordova.apache.org/
Xamarin - http://xamarin.com/
iOS Dev Center - https://developer.apple.com/devcenter/ios/index.action
Android Developer - http://developer.android.com/index.html
Xamarin on GitHub - https://github.com/xamarin
The Mono Project - http://www.mono-project.com/Main_Page
TinyIoC - https://github.com/grumpydev/TinyIoC
TinyMessenger - https://github.com/grumpydev/TinyMessenger
WaveEngine - http://www.waveengine.net/
MonoGame (XNA) - http://monogame.net/
EmguCv (open CV) - http://www.emgu.com/wiki/index.php/Main_Page
NetTopologySuite - http://code.google.com/p/nettopologysuite/
MVVMCross - https://github.com/slodge/MvvmCross
SQLite-Net - https://github.com/praeclarum/sqlite-net
ServiceStack - http://www.servicestack.net/
Xamarin.iOS Bindings - https://github.com/mono/monotouch-bindings
OxyPlot.2DGraphLib - https://github.com/Emasoft/OxyPlot.2DGraphLib.MonoTouch
ShinobiControls - http://blog.xamarin.com/shinobicontrols-joins-the-xamarin-component-store-and-
evolve-speaker-lineup/