Define xPlatform app architecture

[sibille]

Consider:

• Reusability
• Complexity
• Best practices, ...

Figure out which changes will require the current code (if it will be needed to be shared with the xPlat stuff). We found the following approximation:

• Do not use .NET Standard as it will require UWP 16299 as min target
• We will try to predefiene an architecture which allows to share code with UWP native implementations (Core library)
• We are using Shared Projects (as Xamarin team recommendation) to be able to be ported in the future to .NET Standard.
• We are thinking in the following solution structure / app architecture:

Project	Namespace	Main Responsibility
(Shared Lib) WtsAppCrossPlat.Core		Common code shared among UWP Native and Xamarin
	Helpers	Common helpers (Observable, RelayCommand?, Singleton…)
	Strings	Resource shared strings
	Services	Common shared services (interfaces or abstract classes if required) (i.e. Data Access)
	Models	Common shared models (base clases or abstract classes if required)
	ViewModels	Common View Moldes (Some of them would be base classes specialized with specific implementations in other layers)
	…
(Shared Lib) WtsAppCrossPlat.Shared		Contains code shared by mobile projects (Uwp, iOS and Android). Will handle the app initialization and activation for Xamarin projects
	ViewModels	Specialized view models shared between Xamarin forms projects
	Views	Shared views (Xamarin forms based) shared between Xamarin projects
	Services	Specific service implementations among mobile projects (if required) - in example: Storage implementation based on Xamarin
	Models	Shared models among Xamarin forms projects (if required)
	Helpers	Shared helpers among Xamarin forms (if required)
	…
WtsAppCrossPlat.iOS		Specific implementations for iOS under Xamarin forms
	ViewModels	Specializations for ViewModels in iOS
	Views	Specializations for Views in iOS
	Properties
	Services	Specific or concrete implementations of services for iOS (if required)
	Models	Specific or concrete implementations of services for iOS (if required)
	Helpers	Specific or concrete implementations of services for iOS (if required)
	…
WtsAppCrossPlat.Android		Specific implementations for Android under Xamarin forms
	ViewModels	Specializations for ViewModels in Android
	Views	Specializations for Views in Android
	Properties
	Services	Specific or concrete implementations of services for Android (if required)
	Models	Specific or concrete implementations of models for Android (if required)
	Helpers	Specific or concrete implementations of models for Android (if required)
	…
WtsAppCrossPlat.UWP		Specific implementations for UWP under Xamarin forms
	ViewModels	Specializations for ViewModels in UWP
	Views	Specializations for Views in UWP
	Services	Specific or concrete implementations of services for Android (if required)
	Models	Specific or concrete implementations of models for Android (if required)
	Helpers	Specific or concrete implementations of models for Android (if required)

[ralarcon]

We are not going to ship this in v1.5, moving to 2.0 (even we can continue working on it)

[ralarcon]

Finally, we will not be including the Shared Library for Core parts until we need it.

The Xamarin app architecture we will use can be found here (xamarin-infa branch): https://github.com/Microsoft/WindowsTemplateStudio/tree/xamarin-infra/poc/WtsXamarin