Entity framework code-first null foreign key

Question

I have a User < Country model. A user belongs to a country, but may not belong to any (null foreign key).

How do I set this up? When I t

Answer 1

I recommend to read Microsoft guide for use Relationships, Navigation Properties and Foreign Keys in EF Code First, like this picture.

Guide link below:

https://docs.microsoft.com/en-gb/ef/ef6/fundamentals/relationships?redirectedfrom=MSDN

Answer 2

I have the same problem now , I have foreign key and i need put it as nullable, to solve this problem you should put

    modelBuilder.Entity<Country>()
        .HasMany(c => c.Users)
        .WithOptional(c => c.Country)
        .HasForeignKey(c => c.CountryId)
        .WillCascadeOnDelete(false);

in DBContext class I am sorry for answer you very late :)

Answer 3

You must make your foreign key nullable:

public class User
{
    public int Id { get; set; }
    public int? CountryId { get; set; }
    public virtual Country Country { get; set; }
}

Answer 4

I prefer this (below):

public class User
{
    public int Id { get; set; }
    public int? CountryId { get; set; }
    [ForeignKey("CountryId")]
    public virtual Country Country { get; set; }
}

Because EF was creating 2 foreign keys in the database table: CountryId, and CountryId1, but the code above fixed that.