EF 6.1代码优先与不同主键的一对一关系

Question

I am having an issue getting a reference to the employee object from the PayGroup object using Entity Framework 6.1. I have a foreign key in the database on PayGroup.SupervisorId -> Employee.EmployeeId. Note that this is a zero or one-to-one relationship (a pay group can only have one supervisor and an employee can only be the supervisor of one pay group).

According to this post on GitHub , it is not possible to have a foreign key on a table with a different primary key. I've added the foreign key to the database manually but I can't figure out how to set up the fluent api mapping to be able to get the employee object from pay group.

Pay Group Table

Employee Table

Note: There is a foreign key from PayGroup.SupervisorId - Employee.EmployeeId in the database.

Below are the DTO's (I don't currently have any working relationship mapping between these classes):

public class PayGroup
{
    public int Id { get; set; }
    public string SupervisorId { get; set; }
    public virtual Employee Supervisor { get; set; }
}

public class Employee
{
    public string EmployeeId { get; set; }
    public string FullName { get; set; }
}

Answer 1

one-to-one relationship with explicit FK property (like your PayGroup.SupervisorId ) is not supported.

So remove that property from the model:

public class PayGroup
{
    public int Id { get; set; }
    public virtual Employee Supervisor { get; set; }
}

and use the following fluent mapping:

modelBuilder.Entity<PayGroup>()
    .HasRequired(e => e.Supervisor)
    .WithOptional()
    .Map(m => m.MapKey("SupervisorId"));

The WithOptional() call specifies two things. First that there is no inverse navigation property in Employee class, and second that the FK is optional ( Allow Nulls = true in the table).

If you decide to add inverse navigation property

public class Employee
{
    public string EmployeeId { get; set; }
    public string FullName { get; set; }
    public virtual PayGroup PayGroup { get; set; } // <=
}

change it to WithOptional(e => e.PayGroup) .

If you want to make it required ( Allow Nulls = false in the table), then use the corresponding WithRequiredDependent overload ( Dependent here means that the Employee will be the principal and PayGroup will be the dependent ).