title: The type or namespace name 'AspNetCore' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
body: <p>I suddenly start having error in project. all csproj files are correct and all packages are up to date.</p>
  <p>I am working with .net core 5. I have folder structure like below.</p>
  <p>Project
  Project core
  Project business
  Project infrastructure</p>
  <p>Would you please help me solve this?</p>
  <p>Here is the error list</p>
  <p><a href="https://i.stack.imgur.com/izS1u.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/izS1u.png" alt="enter image description here" /></a></p>
  <p>Thank You</p>