If you get such an error from Rider after initial migration dotnet ef migrations add InitialMigration --project DAL --startup-project WebApp that cannot resolve symbol ‘UseIdentityColumns’ then please check that you have nuget package Microsoft.EntityFrameworkCore.SqlServer v5.0.0 installed in DAL (data access layer) class library. I had it missing and could not figure out for some time and Stack Overflow did not have any threads available for it at this point.
I use C# 9, dotnet 5.0 and Rider EAP 2020.3 at the moment. If you use any of the earlier versions of dotnet or C# then please pay attention to getting the correct version of the package.