How to make an OwnsOne property in EF Core 3.0 required when mapping to SQL Server columns?

I reached out to the EF Core team and currently the only way to do this would be to manually change the migration that is created to set nullable = false. It has been flagged as a feature request so let's hope one day they get it fixed!

EF Core 5

In addition to set .IsRequired() on the required properties within the ValueObject, you need to configure the navigation as required after x.OwnsOne(...):

builder.OwnsOne(o => o.Address, a =>
            {
                a.WithOwner();

                a.Property(p => p.Street)                    
                    .IsRequired();

                a.Property(p => p.ZipCode)
                    .IsRequired();

                a.Property(p => p.City)
                    .IsRequired();

            }).Navigation(p => p.Address).IsRequired();
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Issue: https://github.com/dotnet/efcore/issues/12100

Credits to: @AndriySvyryd