System.Data.MetadataException: Unable to load the specified metadata resource

Question

My connection strings are as follows:

Answer 1

We upgraded from .net core 1 to 3.1 and from visual studio 2015 to visual studio 2019. We noticed that the Build Action for some files has been reset. So we changed back the Build Action from None to Content for all files ending with .tt, and their Copy to Output directory to Do Not Copy.
We also had to change the build action of the .edmx file to EntityDeploy and its copy to output directory value to Do Not Copy.
HTH someone.