In a ‘classic’ .NET project, you have an AssemblyInfo.cs file.
This file contains all kind of information about your assembly
After upgrading a classic .NET project to .NET Standard, I started to get errors about some of the properties inside the AssemblyInfo.cs file:
A .NET Standard project already has the AssemblyInfo information built-in. So after upgrading you end up with 2 AssemblyInfo specifications, leading to the errors above.
The solution is to remove the original AssemblyInfo.cs file in the Properties folder.
Remark: If you want to change the assembly information, you now have to use the Package tab inside your Project Properties.