实体框架：一对一/一对一，C＃代码优先

Question

Sorry in advance if this has been answered somewhere, but I searched around and could not find the answer.

I am trying to link up UserProfile and Reviewer tables. Reviewer is a type of users in the application, so the relationship between the two tables is one (UserProfile) to zero/one (Reviewer).

The UserProfile model is:

[Table("UserProfile")]
public class UserProfile
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }
    public string UserName { get; set; }

    public virtual Reviewer Reviewer { get; set; }
} 

Reviewer Class:

public class Reviewer
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
    [ForeignKey("UserProfile")]
    public int ReviewerID { get; set; }

    public string Email { get; set; }
    // other properties of Reviewer...

    public virtual UserProfile UserProfile { get; set; }

}

In other words I am trying to set the foreign key UserId as the key of the table Reviewer, with the name as ReviewerID.

I specify the fluent API as the following:

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

        // other fluent API...

        modelBuilder.Entity<UserProfile>()
                .HasOptional(x => x.Reviewer).WithRequired(x => x.UserProfile);

    }

However, the database generated by Code First is not quite what I wanted.

Suppose I have the following entry in the UserProfile table: UserId = 4, UserName = lostman1

and I try to manually insert a new record to the Reviewer table: ReviewerID = 4, Email = d@d.com

It turns out that I cannot update the ReviewerID field in the database cause it is an auto-incremented field. Moreover, I get the following error:

The data in row 4 was not committed.
Error Source: SQL Server Compact ADO.NET Data Provider.
Error Message: A foreign key value cannot be inserted because a corresponding primary key > value does not exist. [Foreign key constraint name = FK_dbo.Reviewer_dbo.UserProfile_ReviewerID]

Whats wrong with my code first setup? Many thanks!

Answer 1

Seems to me that you need to have a UserID FK relationship between Reviewer and User. In such a design, not all users would have to be reviewers, but all reviewers would have to be a user.

I also am starting to think that maybe you are over-complicating things by no utilizing a concept of roles within your system. Generally, a user vs reviewer would be specified depending upon the roles that a user has. In this manner, all users would be the same and hold the same data in the tables, the only difference would be that the users have different roles.

Authorization and authentication also become simplified when using Roles vs doing complicated table joining or nullable FK relationships.

Answer 2

Not sure if your problem is solved,if not, you can try something like this

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>().HasOptional(x => x.Reviewer).WithRequired(x => x.User).Map(x => x.MapKey("UserId"));
        base.OnModelCreating(modelBuilder);
    }

And here are my model declaration

public class User
{
    [Key]
    public int UserId { get; set; }
    public string UserName { get; set; }

    public virtual Reviewer Reviewer { get; set; }
}
public class Reviewer
{
    [Key]
    public int ReviewerId { get; set; }

    public virtual User User { get; set; }
}