There are many ways to share code between .Net/Xamarin applications running on different platforms, but what is the best way to deal with the platform specific code? In this session you'll learn how to use shared files, dependency injection, portable class libraries, and shared projects to isolate platform specific code from the re-usable shared code.

1. Techniques for Cross
Platform .NET Development
Jeremy Hutchinson
@hutchcodes

2. What is “Cross Platform”
Android Phone
Android Tablet
Android Wear
iPhone
iPad
Apple Watch
Apple TV
Windows Phone
Windows Apps
Microsoft Band
Silverlight
XBox
.Net Core
.Net (ASP, WPF,
Winforms, Etc)

3. Supported Languages and Tools
Shared Logic
Platform A Platform B

5. using Windows.Storage;
namespace XPlat
{
public class UserData
{
public List<TodoItem> GetUserTodoList()
{
var userName = this.UserName;
//Make a call to a cloud resource
}
public string UserName
{
get
{
return ApplicationData.Current.LocalSettings.Values["UserName"].ToString();
}
set
{
ApplicationData.Current.LocalSettings.Values["UserName"] = value;
}
}
}
}

6. Linked Files Shared Project* Portable Class
Conditional Compile  
Partial Classes  
Inheritance   
Dependency Injection   
Share Code
Manage
Platform
Differences
How do we share code?

7. Linked Files

10. Shared Projects

15. UserData.cs
WinPhone8 Project Windows81 Project
Share Project

16. using System.IO.IsolatedStorage;
namespace XPlat
{
public class UserData
{
public List<TodoItem> GetUserTodoList()
{
var userName = this.UserName;
//Make a call to a cloud resource
}
public string UserName
{
get
{
return IsolatedStorageSettings.ApplicationSettings["UserName"].ToString();
}
set
{
IsolatedStorageSettings.ApplicationSettings["UserName"] = value;
}
}
}
}

17. Conditional Compilation
#if DEBUG
public string Foo;
#else
public string bar;
#endif

18. Conditional Compilation

19. #if SILVERLIGHT
using System.IO.IsolatedStorage;
#else
using Windows.Storage;
#endif
namespace XPlat
{
public class UserData
{
public string UserName
{
get
{
#if SILVERLIGHT
return IsolatedStorageSettings.ApplicationSettings["UserName"].ToString();
#else
return ApplicationData.Current.LocalSettings.Values["UserName"].ToString();
#endif
}

20. #if SILVERLIGHT
using System.IO.IsolatedStorage;
#else
using Windows.Storage;
#endif
namespace XPlat
{
public class UserData
{
public string UserName
{
get
{
#if SILVERLIGHT
return IsolatedStorageSettings.ApplicationSettings["UserName"].ToString();
#else
return ApplicationData.Current.LocalSettings.Values["UserName"].ToString();
#endif
}

21. #if SILVERLIGHT
using System.IO.IsolatedStorage;
#endif
#if NETFX_CORE
using Windows.Storage;
#endif
#if __IOS__
using Foundation;
#endif
#if ANDROID
using Android.App;
using Android.Content;
#endif

22. Partial Classes

24. namespace XPlat
{
public partial class UserData
{
public List<TodoItem> GetUserTodoList()
{
//Get the username for local storage
var userName = this.UserName;
//Make a call to a cloud resource
}
}
}

25. using Windows.Storage;
namespace XPlat
{
public partial class UserData
{
public string UserName
{
get
{
return ApplicationData.Current.LocalSettings.Values["UserName"].ToString();
}
set
{
ApplicationData.Current.LocalSettings.Values["UserName"] = value;
}
}
}
}

26. using System.IO.IsolatedStorage;
namespace XPlat
{
public partial class UserData
{
public string UserName
{
get
{
return IsolatedStorageSettings.ApplicationSettings["UserName"].ToString();
}
set
{
IsolatedStorageSettings.ApplicationSettings["UserName"] = value;
}
}
}
}

30. Inheritance

31. namespace XPlat
{
public abstract class UserDataBase
{
public List<TodoItem> GetUserTodoList()
{
//Get the username for local storage
var userName = this.UserName;
//Make a call to a cloud resource
}
public abstract string UserName { get; set; }
}
}

32. using Android.App;
using Android.Content;
namespace XPlat
{
public class UserData : UserDataBase
{
private readonly ISharedPreferences _preferences;
public UserData()
{
var ctx = Application.Context;
_preferences = ctx.GetSharedPreferences(ctx.PackageName, FileCreationMode.Private);
}
public override string UserName
{
get { return _preferences.GetString("UserName", ""); }
set
{
using (var editor = _preferences.Edit())
{
editor.PutString("UserName", value);
editor.Commit();
}
}
}
}
}

33. What do all these have in common?
namespace XPlat
var userData = new XPlat.UserData();
var todos = userData.GetUserTodoList();

34. Dependency Injection

35. namespace XPlat
{
public interface IStoredSettings
{
string UserName { get; set; }
}
}

36. namespace XPlat
{
public class UserData
{
private readonly IStoredSettings _storedSettings;
public UserData(IStoredSettings storedSettings)
{
_storedSettings = storedSettings;
}
public List<TodoItem> GetUserTodoList()
{
//Get the username for local storage
var userName = _storedSettings.UserName;
//Make a call to a cloud resource
throw new NotImplementedException();
}
}
}

37. using Foundation;
namespace XPlat.iOS
{
public class AppleSettings : IStoredSettings
{
public string UserName
{
get { return NSUserDefaults.StandardUserDefaults.StringForKey("UserName"); }
set
{
var defaults = NSUserDefaults.StandardUserDefaults;
defaults.SetString(value, "UserName");
defaults.Synchronize();
}
}
}
}

38. var userData = new XPlat.UserData(new XPlat.iOS.AppleSettings());
var todos = userData.GetUserTodoList();

39. Linked Files Shared Project* Portable Class
Conditional Compile  
Partial Classes  
Inheritance   
Dependency Injection   
Share Code
Manage
Platform
Differences
How do we share code?

40. Jeremy Hutchinson
Blog
hutchcodes.net
Twitter
@hutchcodes
Email
jrhutch@live.com