I\'m using ASP.NET Core 2 with Entity Framework Core 2.0.2. I created a context and Add-Migrations command in Package Manager Controller works fine.
Add-Migrations
How
Just in case somebody lands here who is trying to run System.Data.SqlClient on net50/netstandard on rid freebsd-x64: Microsoft.Data.SqlClient worked for me.
Maybe this works on every portable option and/or for all System.[...] ->Microsoft.[...] dll.