问题
I changed my Asp.Net Core 1.1 application to Core 2.0
This went pretty well but after I updated my nuget packages and I get this error everywhere
The type 'xxx' is defined in an assembly that is not referenced. You must add a reference to assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.
When I press the button to add an assembly nothing happens. I tried rebuilding and restoring my packages multiple times but it won't work
回答1:
I think you are having problem with the reference to the old NETStandard version in your class library. Just make sure you have removed NETStandard reference from all the csproj files in the solution.
来源：https://stackoverflow.com/questions/45699238/problems-with-adding-reference-to-netstandard-2-0