What is the compatibility between a WinRT class library and Windows Phone 8?

Question

I want to have a class library that will run under WinRT and also Windows Phone 8. What do I need to do?

Answer 1

+1 on Cerebrate's answer. portable class libraries is the way to go.

However, PCL aren't a magic wand and won't bridge many of the inconsistencies between WP8 and Win8. For more hardcore code sharing you'll need to consider sharing C# files, adding conditional compilation and many other tricks. Nokia has a great article on WP7 and WP8 code sharing that would apply to this case as well @ http://www.developer.nokia.com/Resources/Library/Lumia/#!co-development-and-porting-guide.html

There's also this great Nokia Wiki article with similar intents @ http://www.developer.nokia.com/Community/Wiki/Maintaining_a_WP7_and_WP8_version_of_a_same_Silverlight_application

Answer 2

To do that, you need to build your class library as a Portable Class Library, which creates an assembly that will run on multiple platforms. (Otherwise, assemblies for WinRT and Windows Phone 8 are essentially non-interchangeable.)

Visual Studio 2012 includes a project type that will let you do this easily; there is also a downloadable toolset that will let do this on VS 2010.

The framework functionality available is limited to a subset of that which is available on all of the platforms you are supporting.

Full details are available from MSDN, here: http://msdn.microsoft.com/en-us/library/gg597391.aspx