Entity Framework - Foreign keys and Navigation Properties

Question

I need your help understanding relationships between tables. I´m having a hard time trying to understand the usage/need of using navigation properties with foreign key properties to define relantionships. Given the 2 classes below,

public class Person
{
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

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

public class Package
{
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

        [Required]
        public Guid AccountId { get; set; }
        public virtual Person Account { get; set; }

        public Guid ShipperId { get; set; }
        public virtual Client Shipper { get; set; }

        [Required]
        public Guid ReceiverId { get; set; }
        public virtual Client Receiver { get; set; }

}

If I try to update the database, I get the error

Introducing FOREIGN KEY constraint 'FK_' on table 'Packages' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

On the other hand if I remove the property public Guid ....Id { get; set; }, the database is created with the foreign keys but the [Required] annotation as no effect.

What´s the difference between including a Guid property and not?

Did you try to put [ForeignKey("AccountId")] on Account property? Here is the tutorial — Serhii
– Serhii, Commented Feb 14, 2021 at 16:45
There are two Id properties. Which one did you remove? I guess it's the one in Person. Please read about the differences in (foreign key) relationships and owned types. — Gert Arnold
– Gert Arnold, Commented Feb 15, 2021 at 8:14
After having done that, please note that there's are tons of questions about this SQL Server limitation on foreign keys. — Gert Arnold
– Gert Arnold, Commented Feb 15, 2021 at 8:20

Serge · Accepted Answer · 2021-02-14 19:29:02Z

try to use this classes:


 public class Person
    {
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

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

        [InverseProperty(nameof(Package.Account))]
        public virtual ICollection<Package> Packages { get; set; }

    }

    public class Package
    {
        
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

        [Required]
        public Guid AccountId { get; set; }
       
        [ForeignKey(nameof(AccountId))]
        [InverseProperty("Packages")]
        public virtual Person Account { get; set; }
    }

and use this code in dbcontext:

modelBuilder.Entity<Package>(entity =>
{
    entity.HasOne(d => d.Person)
    .WithMany(p => p.Packages)
    .HasForeignKey(d => d.AccountId)
    .OnDelete(DeleteBehavior.ClientSetNull);

});

Collectives™ on Stack Overflow

Entity Framework - Foreign keys and Navigation Properties

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related