nuspec contentFiles not added to a project

Question

I have a web project (mvc5) with a project.json inside.

Also, I have a nuget package. Inside this package (besides the dll reference) I have some Conten

Answer 1

This is by design. NuGet packages are no longer supposed to modify the project's source but only add to its built output or build process (in addition to .NET libraries). The content folder for adding sources to the project is only continued to be supported for packages.config based projects since it would be a breaking change for existing projects, but projects using project.json or PackageReference (VS 2017) get the new behaviour.