实体框架：外键

Question

I have 2 model classes:

public class Nurse
{
    public int Id { get; set; }

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

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

    [Required]
    public string AddressLine1 { get; set; }
    [Required]
    public string AddressLine2 { get; set; }
    public string AddressLine3 { get; set; }
    public string AddressLine4 { get; set; }

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

    [Required]
    [Phone]
    public string ContactNumber { get; set; }

    [Required]
    public DateTime DateOfBirth { get; set; }

    [Required]
    public DateTime RegistrationDate { get; set; }


    //Foreign Keys

    public int PaymentId { get; set; }
    [ForeignKey("PaymentId")]
    public virtual Payment Payment { get; set; }


    public int BranchId { get; set; }
    [Required]
    [ForeignKey("BranchId")]
    public virtual Branch Branch { get; set; }
}  // Cls

and

public class Payment
{
    public int Id { get; set; }

    //Type of String instead of to allow for starting zeros
    [RegularExpression("^[0-9]+$")]
    public string SortCode { get; set; }

    [RegularExpression("^[0-9]+$")]
    public string BankAccountNumber { get; set; }

    [RegularExpression("^[0-9]+$")]
    public string ChequeNumber { get; set; }

    public DateTime DateReceived { get; set; }

    public string Notes { get; set; }

    //Foreign Keys
    public int PaymentTypeId { get; set; }
    [Required]
    [ForeignKey("PaymentTypeId")]
    public PaymentType PaymentType { get; set; }

    public int NurseId { get; set; }
    [Required]
    [ForeignKey("NurseId")]
    public Nurse Nurse { get; set; }
}  // Cls

Whenever I try to run the application I get the following error:

Exception thrown: 'System.InvalidOperationException' in EntityFramework.dll

Additional information: The ForeignKeyAttribute on property 'Payment' on type 'PNA_Model.Nurse' is not valid. The foreign key name 'PaymentId' was not found on the dependent type 'PNA_Model.Payment'. The Name value should be a comma separated list of foreign key property names.

Each payment belongs to a nurse but not every nurse has a payment.

If I change the 'Id' property of Payment to 'PaymentId' the error goes away, which kind of makes sense according to the error message.

However I thought EF was smart enough to figure this out itself and I have similar situations with other classes and their 'Id' properties and I'm not getting error messages for them.

Any ideas?

Thanks

Answer 1

OK, I think I found what I was doing wrong.

First of all, Entity Framework requires that in 1-to-1 relationships the Primary Key of the dependent (Payment) must also be the Foreign Key.

So in class 'Nurse' i don't need the 'PaymentId' property because in the Payment class the Key (Payment.Id) will also be the Foreign Key for Nurse and will therefore be equal to the Nurse Key (Nurse.Id). In the Payments class I should remove the 'NurseId' property because this is going to be dealt with in the Key/ForeignKey

I can do the rest in 2 ways.

1. In Payment Class - Use data annotation on the Key (Payment.Id)

    [ForeignKey("Nurse")] public int Id { get; set; } 

2. In PaymentConfig Class -

    HasRequired(p => p.Nurse) .WithOptional(n => n.Payment); 

The 2nd option might be better if you also want to specify

WillCascadeOnDelete(false)

Thanks to all who helped!