Learn about cross-platform approaches to developing native applications using C# and .NET for iOS, Android and Windows Phone 7.

1. Xamarin
Seminar
19th April 2012
Copyright 2012 © Xamarin Inc. All rights reserved

2. Agenda
Cross-Platform Mobile Development
Greg Shackles
Senior Software Engineer
OLO Online Ordering
greg@gregshackles.com
gregshackles.com
@gshackles
github.com/gshackles
Xamarin
Copyright 2012 © Xamarin Inc. All rights reserved

3. Introduction
This session will discuss how to use C# to develop
iOS, Android and Windows Phone applications.
We’ll cover:
•Why use C#?
•Code sharing techniques and patterns
•Useful libraries
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4. Native Platform Languages
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5. Write Once, Run Anywhere?
!= !=
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6. C# to the Rescue!
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7. Benefits
•C# and .NET are mature and powerful
•Skill reuse on all platforms
•Apps are still completely native
•Code can be reused across platforms
(even non-mobile platforms!)
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8. Architecture
Mono#for#
UI# Silverlight# MonoTouch#
Android#
C## Business#Logic#
Run)me# .NET# Mono#
Pla/orm# WP7# iOS# Android#
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9. What Code Can Be Shared?
•Most non-UI or platform code
•Core application logic
•Entities
•LINQ (objects, XML)
•Network access (System.Net)
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10. Requirements
•MonoTouch
•Mac OS X
•MonoDevelop
•Mono for Android
•Mac OS X or Windows
•MonoDevelop or Visual Studio 2010
•Windows Phone
•Windows
•Visual Studio 2010
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11. File Linking
•All profiles are not created equal
•Single copy of file
•Compile-time verification
•Project Linker extension for VS2010
http://msdn.microsoft.com/en-us/library/ff648745
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12. Abstraction
•Separate common logic from UI
•Interfaces, base classes, etc.
public interface IContactManager
{
IList<Person> GetContacts();
}
public class AndroidContactManager : IContactManager
{
public IList<Person> GetContacts()
{
return null;
}
} Xamarin
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13. Library: Xamarin.Mobile
•Abstraction layer over platform APIs
•Contacts
•Geolocation
•Camera
•...
http://xamarin.com/mobileapi
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14. Observer Pattern
•Decouple UI from business logic
•Business layer can publish updates
•UI layer subscribes to updates
public EventHandler<EventArgs> MessageReceived;
MessageReceived += (sender, args) =>
{
Console.WriteLine("Message received");
};
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15. Library: TinyMessenger
•Event aggregator/messenger
•Publish/subscribe
•Single file
•Supports iOS, Android, Windows Phone
https://github.com/grumpydev/TinyMessenger
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16. Partial Classes and
Methods
public partial class MyClass
{
// partial methods are private, and must return void
partial void Foo();
public void Bar()
{
Foo();
}
}
public partial class MyClass
{
partial void Foo()
{
Console.WriteLine("Foo");
}
}
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17. Conditional Compilation
#if __ANDROID__
Console.Write(“Only on Android”);
#elif WINDOWS_PHONE
Console.Write(“Only on Windows Phone”);
#else
Console.Write(“Everything else”);
#endif
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18. Conditional Compilation
•MonoTouch
•No default symbols
•Mono for Android •Windows Phone
•__ANDROID__ •WINDOWS_PHONE
•__ANDROID_1__ •SILVERLIGHT
•__ANDROID_2__
•...
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Copyright 2012 © Xamarin Inc. All rights reserved

19. File Access
•Direct file access
•System.IO
•Works on iOS and Android
•Not supported by Windows Phone
•Paths are different on iOS and Android
File.WriteAllText(
Environment.GetFolderPath(Environment.SpecialFolder.Personal),
"Writing directly to a file");
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20. File Access
•Isolated Storage
•Works on iOS, Android, and Windows Phone
•Higher level API
•Don’t need to worry about file paths
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var writer = store.OpenFile("MyFile", FileMode.Create))
{
// write to the file
}
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21. Database Access
•iOS and Android
•SQLite
•Native APIs or ADO.NET
•Windows Phone
•SQL Server CE
•LINQ to SQL
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22. Library: C#-SQLite
•C# port of SQLite database
•File based
•Useful for Windows Phone, Silverlight
http://code.google.com/p/csharp-sqlite
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23. Library: sqlite-net
•Layer over SQLite database
•Strongly-typed queries
•Single file
•Supports iOS, Android, Windows Phone
http://code.google.com/p/sqlite-net
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Copyright 2012 © Xamarin Inc. All rights reserved

24. Library: TinyIoC
•Inversion of Control container
•Single file
•Supports iOS, Android, Windows Phone
https://github.com/grumpydev/TinyIoC
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25. Library: MonoCross
•Cross-platform MVC framework
•Shared models and controllers
•Views specific to platforms
•Supports iOS, Android, Windows Phone
•Sits atop MonoTouch, Mono for Android
http://code.google.com/p/monocross/
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Copyright 2012 © Xamarin Inc. All rights reserved

26. More Links
MWC 2012 App
https://github.com/xamarin/mobile-samples/tree/master/MWC
NYC Code Camp 6 App
https://github.com/gshackles/NycCodeCamp6
Mobile Development in C#
http://amzn.com/1449320236
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Copyright 2012 © Xamarin Inc. All rights reserved

27. Xamarin
Seminar
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19th April 2012
Copyright 2012 © Xamarin Inc. All rights reserved