实体框架配置为“必需到可选”关系

Question

I'm having some problems with what I thought should be a simple EF relationship. I have an Email entity which has a ModerationResult Navigation property, and the ModerationResult entity has a ManualModerationReason Navigation property.

public class Email
{
    public int EmailId { get; set; }
    public ModerationResult ModerationResult { get; set; }
    ...
}

public class ModerationResult
{
    public int ModerationResultId { get; set; }
    public ManualModerationReason ManualModerationReason { get; set; }
    ...
}

public class ManualModerationReason
{
    public int ManualModerationReasonId { get; set; }
    public string Reason { get; set; }
    ...
}

The configuration we have for the Email and ModerationResult is working fine. An Email can have ZERO or ONE ModerationResult associated with it. The result of this in our DB is that we have a ModerationResult table which has a field 'Email_EmailId' to relate to the relevant Email.

The next part is where I'm having problems. I've added a new ManualModerationReason Navigation property to ModerationResult. A ModerationResult can have ZERO or ONE ManualModerationReason associated with it.

I've created the DbSet configuration for this new ManualModerationReason entity, and the DB now has a ManualModerationReason table comprising of the 2 fields (ManualModerationReasonId and Reason). This is essentially a lookup table.

public DbSet<ManualModerationReason> ManualModerationReason { get; set; }

I've tried various configurations for the mapping between the ModerationResult entity and its new ManualModerationReason property, but none are working as desired. For example, when I've retrieved a ManualModerationReason object from the Db, then assigned that object to the Email.ModerationResult.ManualModerationReason property, and SavedChanges, I've ended up with a new record in the ManualModerationReason lookup table, and the ForeignKey field in my ModerationResult table (ManualModerationReason_ManualModerationReasonId) remains NULL!

Can anyone please shed any light on what the correct Fluent configuration should be for this requirement? This is how it currently looks in my most recent failed attempt:

modelBuilder.Entity<ModerationResult>().HasOptional( m => m.ManualModerationReason );

UPDATE: As requested, this is currently how the saving code looks:

public void Save( Email email )
{
    using ( var ctx = new ModerationContext() )
    {
        ctx.Entry( email ).State = email.EmailId == 0 ? EntityState.Added : EntityState.Modified;

        if ( email.ModerationResult != null )
        {
            ctx.Entry( email.ModerationResult ).State = email.ModerationResult.ModerationResultId == 0 ? EntityState.Added : EntityState.Modified;

            if ( email.ModerationResult.ManualModerationReason != null )
            {
                ctx.Entry( email.ModerationResult.ManualModerationReason ).State = EntityState.Modified;
            }
        }

        ctx.SaveChanges();
    }
}

Answer 1

Don't you think you are missing the navigational property in ManualModerationReason class?

public class ModerationResult
{
   public int ModerationResultId { get; set; }

   public int ManualModerationReasonId { get; set; }

   [ForeignKey("ManualModerationReasonId ")]
   public ManualModerationReason ManualModerationReason { get; set; }

}

public class ManualModerationReason
{
       public int ManualModerationReasonId { get; set; }
       public string Reason { get; set; }

       public List<ModerationResult> ModerationResults { get; set; }

}


modelBuilder.Entity<ManualModerationReason>()
            .HasMany(mreason => mreason.ModerationResults)
            .WithOptional(mresult => mresult.ManualModerationReason)
            .HasForeignKey(mresult => mresult.ManualModerationReasonId);