Question

I have 2 Entities User and User_Profile (one to one relationship). I have linked them as follows:

public class User
{
   [Key]   
   [ForeignKey("user_profile")]
   public int user_id {get;set;}

   public string username {get;set;}
   public string email {get;set;}

   public virtual User_Proile user_profile {get;set;}
}


public class User_Profile
{
   [Key]   
   public int user_id {get;set;}

   public string firstname {get;set;}
   public string lastname {get;set;}
}

user_id is a PK in both SQL Server’s User and User_Profile tables. It is also set as an Identity column in the User table.

When I try to insert a new record via the EFDBContext Add/SaveChanges. I get the following error: “user_id cannot be NULL in the User_Profile table” This makes perfect sense as this is a PK column. I was hoping EF would be able to take the Identity user_id from Users and Insert it into User_Profile user_id when saving.

Is this possible and if so how would I implement that?

UPDATE: Please note that I manually created the DB tables and code classes so I dont have access to StoreGeneratedPattern via the .edmx file.

Answer 1

I think it is necessary to configure your one-to-one relationship explicitely using Fluent API:

public class MyContext : DbContext
{
    // ... your DbSets

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>()
            .HasRequired(u => u.user_profile)
            .WithRequiredPrincipal();
    }
}

And the entity classes:

public class User
{
    [Key]   
    public int user_id {get;set;}
    public string username {get;set;}
    public string email {get;set;}
    public virtual User_Profile user_profile {get;set;}
}

public class User_Profile
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int user_id {get;set;}
    public string firstname {get;set;}
    public string lastname {get;set;}
}

It’s necessary to switch off DatabaseGeneratedOption from Identity to None in one of the classes. I have swapped principal and dependent as it seems that the User should be the principal. The [ForeignKey(...)] is not necessary because EF will recognize user_id in User_Profile as a FK property to User.

A code like this…

using (var context = new MyContext())
{
    var user = new User();
    var userProfile = new User_Profile();

    user.user_profile = userProfile;

    context.Users.Add(user);
    context.SaveChanges();
}

…should work then as you expect and save both related entities to the database.