I believe I had the same issue as you did. I didn’t save the whole error message, but my error message was
‘Could not load file or assembly ‘Microsoft.Build.Framework,
Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or
one of its dependencies. The system cannot find the file specified.‘
I am using Visual Studio 2017 and was trying to do Update-Database
after Add-Migration
.
To resolve the issue I closed Visual Studio and re-opened it, then re-ran Update-Database
again.
This may or may not resolve your issue, but I thought I’d post just in case it would help.