This project references NuGet package(s) that are missing on this computer

Question

I have an ASP.NET MVC5 application that worked yesterday and now I am getting this error when I try to build:

This project references NuGet package(s)

Answer 1

I had this when the csproj and sln files were in the same folder (stupid, I know). Once I moved to sln file to the folder above the csproj folder my so