According to the Visual Studio 2015 Preview documentation, VS 2015 adds templates for shared projects and a UI for managing the references, so the below should no longer be necessary after upgrading.

There does not seem to be a way to create one directly. It appears currently that Shared Code projects are automatically created when you create a Universal App project as shown in this introduction to creating a Universal App.

Therefore, to create one in your solution: Add a new project type "Blank App (Universal App)." Delete the Windows 8 and Windows Phone projects it created leaving only the Shared project.

通过以上意思，表示非手动创建，而是在创建Universal App时自动创建的.