.NETPortable

Your project is not referencing the ".NETPortable,Version=v4.5,Profile=Profile259" framework. Add a reference to ".NETPortable,Version=v4.5,Profile=Profile259" in the "frameworks" section of your proj
NUGET PCL vs2017 .NETPortable Version=v4.5 Profile=Profile259 project.json frameworks
04-11