Share code base for WP7 and WP8

Question

I'm working on architecture of new business application targeting WP7 and WP8. For WP7 we will use silverlight app model and want to be prepared to reuse the code while moving to WP8 (we will want to use additional features on WP8).

Since WP8 will also support xaml and C# do you have any special recommendations how to organize app structure, select appropriate methodology.

To summarize recommendations below:

Separate code and UI.
For business logic you can use C# Windows Phone Class Library (7.1 to work for both WP7 and WP8)
Consider using the Task Parallel Library for Windows Phone, if you do a lot of async.
Use separate lib for WP8 specific features. Connect it to WP8 only.
You may want to move common UI to separate lib since it should be supported in both Wp7 and Wp8 (according to my experiments).

Just to make it clear, the application model (for all you would care), for WP7 and WP8, is *exactly the same*. — Claus Jørgensen, Jun 24 '12 at 19:57
Just tried to compile some WP7.1 application using VS Express 2012 Beta for Windows Phone. After setting target to WP8 everything compiled out of the box including UI controls, unfortunately unable to test in WP8 emulator due to not supported hardware. Added await C# 5.0 language feature to existing code - seems to compile fine. — Sergei Grebnov, Jun 25 '12 at 14:32
We haven't released the SDK yet, so what are you talking about? — Claus Jørgensen, Jun 25 '12 at 16:34
Early access to Windows Phone PROTOTYPE developer tools (Microsoft Connect program) — Sergei Grebnov, Jun 25 '12 at 20:14
Oh, have fun with that then :p And get some hyper-v supported hardware, you'll need it. — Claus Jørgensen, Jun 25 '12 at 21:19

score 4 · Accepted Answer · answered Jun 24 '12 at 19:24

how to organize app structure, select appropriate methodology.

Well, MVVM is always a hit when working with Windows Phone. Any good clean structure, following SOLID principles will do just fine.

Windows Phone 8 will support the new C# 5.0 language features, so if you have a lot of asynchronous code, consider using the Task Parallel Library for Windows Phone for Windows Phone 7, since all calls returning Task will support the new await operator in C# 5.0.

The most important change in Windows Phone 8 is new, and better performing controls. If you want to support both platforms with the same code-base, you want to try separate your UI code as much as possible from the rest of the application. Most likely you'll want to separate UI logic, such as ViewModels, as well.

Consider having at least one separate assembly for your business logic, that handles data query operations and/or calculations.

As for new features, like C++ development / WinRT interop, that'll be done though separate assemblies, which you only can reference from your Windows Phone 8 assemblies anyway; which means it shouldn't provide any concerns for your current application structure.

Thank you Claus, like the idea of using Task Parallel Library — Sergei Grebnov, Jun 25 '12 at 14:20

score 2 · Answer 2 · answered Jan 02 '13 at 23:06

The current answers doesn't seem to go into detail on how the actual project structure might look like, so I thought I might share mine here:

What you can see below is the structure for my app which exists in 4 versions: (WP7,WP8)X(Pro,ad funded)

The code and the output folders (bin7, bin8,...) are placed in the first sub directory. The project files are placed in appropriately named subdirectories. The code files and assets are linked into the single projects. The files in the "Properties" folders are special to each version (other GUID, name, live tile icons etc). That way I have to hit once F6 and I have all XAPs for my current version. (Just have to collect them with a little script)

(FYI the "Pro" version is implemented with a #ifdef compiler flag.)

My WP7+WP8(+"PRO"-version) project structure

Thanks for sharing your experience. How do you handle namespaces in xaml? For instance, Pivot was moved from `clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls` to `clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone`. — altso, Jan 21 '13 at 21:37
To be true: currently not at all. The old XAML namespace still seems to work fine... — Hades32, Jan 22 '13 at 22:25

score 0 · Answer 3 · answered Jun 24 '12 at 15:31

Silverlight is a framework based on C#, you are mixing languages and frameworks in your post, the only thing to consider is that WP7 only support C# 3.0 features, WP8 probably will be a more advanced workbench with DirectX and C# 4 or better, we don't know yet, but with WP8 also comes in the full support for C and C++.

Silverlight does not receive significant updates or news from a long time. If you really want to target this 2 OS i suggest to use a shared C# 3.0 codebase, avoiding the use of Silverlight as much as possible, and probably could be a better choice thinking to the fact that the WP7 devices are pratically dead in terms of updates and core features; they are Silverlight-based device with XNA for games, but some hardware related features are very low-end, plus Microsoft is not speaking about Silverlight for a long time and this new updates about the C/C++ support could be a game-changer for a developer.

Also there is C# 5.0 on the way, a WP7 is already old, it could be older in weeks, also i don't know the details of your project but you probably have to plan some months/weeks doing support and various fixes, i think that you probably should have a very good reason to start a C# 3.0 project targeting a WP7 platform, i'm not discussing WP7 as OS, i'm discussing the convenience of doing what you are planning considering the immediate future and the lack of support and news on some projects from Microsoft.

Stay in touch with the team in Microsoft that talks about this things https://twitter.com/#!/wpdev and see if you can get a much more detailed picture.

In the end keep in mind that probably the only one thing in common that worth considering is the support for the C# 3.0 language, the frameworks may vary or could be more convenient to adopt the new ones, also with C/C++ you get an infinite amount of new libraries for everything.

can you provide a reference fot WP7 supporting C# 4? Also for what you are saying the support is only a partial support. — user827992, Jun 24 '12 at 19:19
C# 4.0 features such as Covariance and Contravariance is supported, same is optional parameters. Why provide a reference, when anyone who can press compile, can see it's true. (Sorry, the previous comment went FUBAR) — Claus Jørgensen, Jun 24 '12 at 19:24
Also, Silverlight 5 was released in December. But the Silverlight 5 features are not relevant to neither WP7 nor WP8. — Claus Jørgensen, Jun 24 '12 at 19:27
WP7 was released 1 and a half year ago, in the late 2010, can you provide a documented example or a link to ensure us about what you are saying? — user827992, Jun 24 '12 at 19:45
How about you go open Visual Studio, and try to compile a Windows Phone project using optional parameters (a C# 4.0 feature *cough*) — Claus Jørgensen, Jun 24 '12 at 19:47
This is not about VS, VS also include a _virtual_ environment, i think that you are not sure about what you are saying. — user827992, Jun 24 '12 at 19:50
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/12970/discussion-between-claus-jorgensen-and-user827992) — Claus Jørgensen, Jun 24 '12 at 19:51

Share code base for WP7 and WP8

3 Answers3