In the new project system, the static contentFiles from Nuget packages are linked and shown in the solution explorer.

The old project system should do the same.

Note that CommandStuff.cs is the only element from the package above the needs shown.
It's also marked as a link.

The example illustrates the difference in 15.7 P3.
ClassLibrary1 is legacy, ClassLibrary39 is SDK csproj.

Additionally it's important that these files are read-only.
Related issue to make them read-only in new project system - #2141

As more and more people are moving their projects as part of the effort in NuGet/Home#5877, this becomes more and more important.

//cc @rrelyea @anangaur @davkean