一对零或一个关系实体框架

Question

I am trying to enforce a one to (zero or one) table relationship using code first/fluent api and the intended table is as below.

Student may only have a contact (StudentContact) or not But Every contact (StudentContact) must have a Student

StudentID StudentName
1         StudentA
2         StudentB

StudentContactID StudentContact StudentID
1                123456789      1
2                123456789      2

I tried to use

EntityName<Student>().HasOptional(x => x.StudentContact).WithRequired(l => l.Student)

but unfortunately it does not enforce a one relationship for StudentID column, meaning that StudentID column may contain duplicate value.

reference: One to zero/one relation in entity framework code first

Answer 1

When you are configuring one-to-one relationships, Entity Framework requires that the primary key of the dependent ( StudentContact ) also be the foreign key. The proper way to achieve what you want could be this, but is using Data Annotations:

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }

    public StudentContact StudentContact { get; set; }
}

public class StudentContact
{
    [Key, ForeignKey("Student")]
    public int StudentId { get; set; }
    public int Contact { get; set; }
    public Student Student { get; set; }
}