Reference a class library from UWP and ASP.NET 5

Question

I am trying to create a class library that'll contain common objects (mainly DTOs) of a WebAPI (using ASP.NET 5) and a consuming UWP App. However, I have not yet figured out how to create the class library such that it can be referenced from both other projects.

What I have tried so far:
First, I tried a Class Library (Package), which can be found under Web. This type of library can be referenced from the ASP.NET project without problems, but when trying to reference it from the UWP project, I get the following message:

A reference to 'ClassLibrary1' could not be added. 

Next, I tried a Class Library (Windows Universal), which can be found under Windows > Universal. This can easily be references from the UWP project, but when trying to reference it from ASP.NET, I get:

The following projects are not supported as references : 

  - The project ClassLibrary2 has a target framework that is incompatible or has version higher than the current project and cannot be referenced.

So: How can I create a class library that can be used in both an ASP.NET 5 project and an UWP project?

Answer 1

What you need is a Portable Class Library (under Windows).

Since you're only targetting ASP.NET 5 and Windows 10, you can limit the platforms to these two only, but there's no "error" in supporting more platforms (it can limit how much of the shared API is available though).