Entity Framework 1:1 relationship Code First - ef-code-first

Question

I'm struggling here. I've tried through data annotations and via the Fluent API and still not working correctly. Desperate for help now. Basically, I have two tables. A Company table and an Address Table. A company must have a head office address (which should live in the Address Table) and an Address must have a Company which is belongs too. I'm really struggling to set this up correctly.
I'll put the Code First Entities then show what I have already got.
[Table("Address")]
public class Address
{
[Key]
public long AddressId { get; set; }
public string Address1 { get; set; }
public string Address2 { get; set; }
public string Address3 { get; set; }
public string Address4 { get; set; }
public string Address5 { get; set; }
public string Town { get; set; }
public string County { get; set; }
public string Country { get; set; }
public string PostCode { get; set; }
public virtual Company Company { get; set; }
public DateTime? RemovedDate { get; set; }
public long? RemovedBy { get; set; }
}
[Table("Company")]
public class Company
{
[Key ]
public long CompanyId { get; set; }
public string Name { get; set; }
public string WebsiteUrl { get; set; }
public virtual Address Address { get; set; }
public User LeadUser { get; set; }
public DateTime ActiveSince { get; set; }
public DateTime? ActiveTill { get; set; }
public string VatRegistration { get; set; }
public string LicenseKey { get; set; }
public LicenseStatus LicenseStatus { get; set; }
public bool CanAgreementBeExtended { get; set; }
public string BillingEmail { get; set; }
public string PhoneNumber { get; set; }
public string MobileNumber { get; set; }
public DateTime DateCreated { get; set; }
public DateTime DateUpdated { get; set; }
public virtual ICollection<User> Users { get; set; }
public virtual ICollection<LicenseHistory> LicenseHistories { get; set; }
}
//Seeded data inserted as follows
var testCompany = new Company
{
ActiveSince = DateTime.UtcNow,
Name = "Test Company",
LeadUser = adminUser,
DateCreated = DateTime.UtcNow,
DateUpdated = DateTime.UtcNow,
BillingEmail = "admin#test.co.uk",
CanAgreementBeExtended = true,
LicenseStatus = LicenseStatus.PendingAgreement,
MobileNumber = "1234567890",
PhoneNumber = "1234567890",
VatRegistration = "1234567890"
};
context.Companies.AddOrUpdate(u => u.Name, testCompany);
var testAddress = new Address
{
Address1 = "Test Ltd",
Address2 = "1 Test Gardens",
Address3 = "Test Heath",
Address4 = string.Empty,
Address5 = string.Empty,
County = "Test",
Town = "Test",
Country = "United Kingdom",
PostCode = "TE5 T11",
Company = testCompany
};
context.Addresses.AddOrUpdate(u => new { u.AddressId }, testAddress);
testCompany.Address = testAddress;
context.Companies.AddOrUpdate(u => u.Name, testCompany);
//Fluent API set up as follows in the OnModelCreating
modelBuilder.Entity<Address>()
.HasRequired(ad => ad.Company)
.WithOptional(s => s.Address);
Can anyone spot what I'm doing wrong? I've been playing round with different combinations for the past few days and it just doesn't work. I just keep getting errors, the latest error based on the code above is...
A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'AddressId'.
Any ideas please?

Answer 1

You can't have a true one to one in SQL Server (see How do I create a real one-to-one relationship in SQL Server), but there is a workaround in EF where you make the primary key of the second entity also a foreign key:
// [Table("Company")] -- not needed unless different
public class Company
{
// [Key ] -- will be key by convention
public long CompanyId { get; set; }
...
public virtual Address Address { get; set; }
}
public class Address
{
[Key, ForeignKey("Company")]
public long AddressId { get; set; }
public string Address1 { get; set; }
...
public virtual Company Company { get; set; }
}
You can also do it with fluent code like:
modelBuilder.Entity<Company>()
.HasRequired(t => t.Address)
.WithRequiredPrincipal(t => t.Company);