User126029 postedI was fixing a warning I was getting and it somehow fixed error too.
The warning I got was:
All projects referencing Core.csproj must install nuget package Microsoft.Bcl.Build.
For more information, see http://go.microsoft.com/fwlink/?LinkID=317569
To solve this, I was referencing this post:
https://forums.xamarin.com/discussion/30464/microsoft-bcl-build-in-external-libraries-wont-compile
And I put <Properties>SkipValidatePackageReferences=true</Properties>
in my main csproj file where it was referencing the Core.csproj project.
The weird thing was, it didn't get rid of this warning above but now I can Run Code Analysis on Solution. Weird.