Shows how to separate code to allow for maximum code reuse across iOS, Android, Windows Phone, Windows Store, WPF, and silverlight applications. Code can be found here: https://github.com/rossdargan/Talks

1. Cross Platform Mobile
Development in C#
Ross Dargan
@rossdargan

2. What I’m going to cover
Target 95% of the UK mobile market in C#
With maximum code re-use

3. What I’m going to cover

4. What I won’t cover
The other cross platform options
(http://propertycross.com/)
A full walkthrough of the tooling
Blackberry

5. Android
56%
Windows
12%
iOS
27%
Blackberry
4%
Other
1%
Other
5%
UK Smartphone Landscape
Source: http://bit.ly/19d2thf

6. Native Development
iOS
Objective C
Xcode
Windows Phone
C#/Visual Basic/F#
Visual Studio
Android
Java
Eclipse
IntelliJ

7. Xamarin
• C# and .NET for Android, iOS and Mac
• Full native APIs

8. The bad…
• Price $2000 per dev per year
• Still need a mac
• Write once, run (and test!) everywhere
• Tooling is still a bit immature (but the
support is great!)
• Need to write each UI separately

9. UI Considerations

10. DEMO
Hello World

11. So… Sharing

12. SHARING CODE
File Linking

13. File Linking

14. DEMO
File Linking

15. File Linking
Pros
• Quick
Cons
• Messy code
• Progressively more
difficult to maintain as you
add implementations
• Very hard to test
• File linking is a PITA to
remember as you add
files

16. SHARING CODE
Portable Class Libraries

17. Adding a PCL

18. Great… but
Still need platform specific code somehow…

19. SHARING CODE
Abstract Classes

20. Multiple Concrete Classes

21. DEMO
Abstract Classes

22. Abstract Classes
Pros
• Quick
• Easier to maintain
• Follows Open/Closed
principal
Cons
• Difficult to test
• Pretty inflexible

23. SHARING CODE
Dependency Injection

24. Dependency Injection
• Helps separate code (Single responsibility)
• Allows you to unit test’s discrete parts of
the implementation – no God classes
• You can inject in platform specific
implementations
• Inversion of Control allows you to swap
implementations easily

25. DEMO
PCL & DI demo

26. Dependency Injection
Pros
• Very loosely coupled
code (reuse)
• Unit tests are easy
• Single Responsibility
• Open/Closed
Cons
•
•
•

29. What are the downsides to using
Dependency Injection?
It can be dangerous for your career because it
may increase your overall knowledge of good API
design. Once you learn how proper loosely
coupled code can look like, it may turn out that you
will have to decline lots of job offers because you
would otherwise have to work with tightly
coupled legacy apps. Happens to me a lot :)
Source: http://bit.ly/com6aD

30. Dependency Injection
Pros
• Very loosely coupled
code (reuse)
• Unit tests are easy
• Single Responsibility
• Open/Closed
Cons
• More code
• Bloated constructors

32. Can we squeeze any more reuse
out?

33. MAXIMIZE UI CODE REUSE
MVVM

34. MVVM
Platform Specific Code
Shared Code

35. Demo

36. Improving Code Reuse in 3 easy
ways
• Heavy use of dependency injection
– Allows different implementations for different
platforms
• Use PCLs (and file linking for the time
being)
• Use View Models to reuse presentation
code

37. 3 layers of win
MVVMCross
Xamarin
Visual Studio

38. Links
• http://xamarin.com/
• http://mvvmcross.wordpress.com/
• http://propertycross.com/
• https://github.com/rossdargan/Talks
• Dependency Injection in .Net by Mark
Seemann (ISBN: 1-935182-50-1)
• http://www.icndb.com/api/

39. Questions