通过Entity Framework 5将复杂模型保存到DB

Question

Given the following code, I am trying to save the complex object Institution to the db. If I take out references to address the base institution saves correctly but with the Address added in I get a foreign key error and nothing saves. What is the correct way to save a complex class?

   Institution inst = new Institution();
   inst.Name = "Institution Name";
   Address address = new Address();
   address.Street1 = "1234 west main";      
   address.City = "Gotham";
   address.State = "WI";
   address.PostalCode = "55555";

   List<Address> addresses = new List<Address>();
   addresses.Add(address);
   inst.Addresses = addresses;              
   db.Institutions.Add(inst);
   db.SaveChanges();

The institution class:

 public class Institution
{
    [Key]
    public int ID { get; set; }
    [Display(Name="Institution Name")]
    public string Name { get; set; }
    public virtual ICollection<Address> Addresses { get; set; }
}

The address class:

 public class Address
{
    [Key]
    public int Id { get; set; }
    [Display(Name = "Street")]
    public string Street1 { get; set; }
    [Required]
    public string City { get; set; }
    [Required]
    [MaxLength(2)]
    public string State { get; set; }
    [Display(Name = "Zip")]
    public string PostalCode { get; set; }
    public virtual Institution Institution { get; set; }
    public virtual AddressType AddressType { get; set; }
}

Answer 1

You can control the one-to-many relationship (and the foreign key definition) by overriding the OnModelCreating in your DbContext. Something similar to the following should work:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Institution>().HasMany<Address>(i => i.Addresses)
        .WithRequired(i => i.Institution).HasForeignKey(i => i.Id);
}

Answer 2

Define Institution with the a constructor.

public class Institution
{
    public Institution()
    {
            Addresses = new Addresses<Student>();
    }

    [Key]
    public int ID { get; set; }
    [Display(Name="Institution Name")]
    public string Name { get; set; }
    public virtual ICollection<Address> Addresses { get; set; }
}

Then you can write your add code like the following

  Institution inst = new Institution();
   inst.Name = "Institution Name";
   Address address = new Address();
   address.Street1 = "1234 west main";      
   address.City = "Gotham";
   address.State = "WI";
   address.PostalCode = "55555";

   inst.Addresses.Add(addresses);              
   db.Institutions.Add(inst);
   db.SaveChanges();