Entity Framework Mapping relationship with Entity Framework Code First: One-to-many and Many-to-many Mapping zero or one-to-many
Example
In the previous examples a car cannot exist without a person. What if you wanted the person to be optional from the car side? Well, it's kind of easy, knowing how to do one-to-many. Just change the PersonId in Car to be nullable:
public class Car
{
public int CarId { get; set; }
public string LicensePlate { get; set; }
public int? PersonId { get; set; }
public virtual Person Person { get; set; }
}
And then use the HasOptional() (or WithOptional(), depending from which side you do the configuration):
public class CarEntityTypeConfiguration : EntityTypeConfiguration<Car>
{
public CarEntityTypeConfiguration()
{
this.HasOptional(c => c.Owner).WithMany(p => p.Cars).HasForeignKey(c => c.OwnerId);
}
}
