visual studio - Why getting Intelligence error in VS 2019

Question

First, I update the VS 2019. After that I updated my project from .net framework 4.6 to 4.8.

Now I getting the Intelligence error in the MVC view. I check some article and blog related it and try below points for it.

1. Delete the bin and obj folder.
2. Delete .vs file
3. Delete the packages folder.

I did all things but still I am getting the same Intelligence error.

Answer 1

I was getting the same error after the framework upgrade. Need to add System.Core reference in the main Web.config file.

<compilation>
  <assemblies>
    <add assembly="System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
  </assemblies>
</compilation>