EF Core 2 mapping relationships

Question

public class MobilePhone{
    public int Id {get; set;}
    public string Name { get; set; }
    public Owner Owner { get; set; }
}

public class Owner{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public ICollection<City> Cities { get;  set; }
}

public class City
{
    public int Id {get; set;}
    public string Name { get;  set; }        
    public Owner Owner { get;  set; }
}


public class OwnerConfiguration : IEntityTypeConfiguration<Owner>
{
    public void Configure(EntityTypeBuilder<Owner> builder)
    {
        builder.ToTable("Owner");
        builder.HasKey(x => x.Id);
        builder.Property(x => x.Id).HasColumnName("Id").ValueGeneratedOnAdd();
        builder.Property(x => x.FirstName);
        builder.Property(x => x.LastName);
        builder.HasMany(x => x.Cities);
    }
}

Do I need to set PK explicitely or it will be set by convention?

What is the proper way to map City and MobilePhone classes?

Answer 1

The Entity Framework convention for primary keys is:

Your class defines a property whose name is “ID” or “Id” or a class name followed by “ID” or “Id” To explicitly set a property to be a primary key, you can use the HasKey method. In the following example, the HasKey method is used to configure the InstructorID primary key on the OfficeAssignment type.

    modelBuilder.Entity<OfficeAssignment>().HasKey(t => t.InstructorID);