You can try using the .IsRequired() method when configuring the OpeningHours property.

internal class LocationConfiguration : IEntityTypeConfiguration<Location>
{
    public void Configure(EntityTypeBuilder<Location> builder)
    {
        builder
            .Property(l => l.Name)
            .IsRequired(); // Assuming Name is required

        builder.OwnsMany(
                l => l.OpeningHours, ownedNavigationBuilder =>
                {
                    ownedNavigationBuilder.ToJson();
                    ownedNavigationBuilder.OwnsMany(o => o.Intervals);
                    ownedNavigationBuilder.WithOwner();
                });
    }
}

Make sure that the Name property in the Location class is marked as required if it is indeed a required field.

Generate a new migration to apply the changes to your database:

dotnet ef migrations add UpdatedLocationConfiguration

Then, update the database:

dotnet ef database update

Second implementation

• In your Location class, you can use the [Required] attribute to specify that the OpeningHours collection is required.

public class Location
{
     public Guid Id { get; set; }

     [Required]
     public string Name { get; set; }

     public ICollection<OpeningHours> OpeningHours { get; set; } = new List<OpeningHours>();
}

• In your DbContext class, you can override the OnModelCreating method and specify the configuration for OpeningHours using HasMany and WithOne .

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Location>()
        .HasMany(l => l.OpeningHours)
        .WithOne();
}

• Ensure that you have a correct JSON converter registered for EF Core. This can be done using the UseJson extension method.

ownedNavigationBuilder.Property(o => o.Intervals)
     .HasConversion(
         v => JsonSerializer.Serialize(v, null),
         v => JsonSerializer.Deserialize<ICollection<TimeInterval>>(v, null)
     )
     .HasColumnType("jsonb"); // Use the appropriate SQL type for your database