CODEWITHSUNDEEP
entity-frameworkmappingef-code-firstforeign-key-relationshipentity-framework-4.1
Shawn Mclean
Shawn Mclean

Reputation: 57469

Entity framework code-first null foreign key

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 try to insert a user with a null country, it tells me that it cannot be null.

The model is as follows:

 public class User{
    public int CountryId { get; set; }
    public Country Country { get; set; }
}

public class Country{
    public List<User> Users {get; set;}
    public int CountryId {get; set;}
}

Error: A foreign key value cannot be inserted because a corresponding primary key value does not exist. [ Foreign key constraint name = Country_Users ]"}

Upvotes: 143

Views: 162958

Answers (5)

Jonathan Moy
Jonathan Moy

Reputation: 438

In EF 7 :

entity.Property(e => e.propertyName).IsRequired(false);

Upvotes: 5

Anonimys
Anonimys

Reputation: 696

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

enter image description here

Guide link below:

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

Upvotes: 0

user1040323
user1040323

Reputation: 501

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.

Upvotes: 15

Yaman Melhem
Yaman Melhem

Reputation: 149

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 :)

Upvotes: 9

Ladislav Mrnka
Ladislav Mrnka

Reputation: 364249

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; }
}

Upvotes: 218

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