Entity Framework one to many with condition - entity-framework

Question

I have a Job class
[Table("Jobs")]
public class Job
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Column("fID")]
public int ID { get; set; }
public virtual ICollection<Note> Notes { get; set; }
}
The note class looks like this:
[Table("Note")]
public class Note
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Column("fID")]
public int ID{get; set;}
[Column("fld_int_NoteTypeID")]
public int NoteTypeID { get; set; }
}
Whenever I request the Notes from a job like this:
var job= context.Jobs.Include(x => x.Notes).FirstOrDefault(x => x.ID == jobId);
I would like the query to implicitly add Where NoteTypeId == 8.
Is it possible to somehow add this clause or do I have to explicitly add it each time?

Answer 1

What about workaround? Add NotMapped property which filters Notes collection:
[Table("Jobs")]
public class Job
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Column("fID")]
public int ID { get; set; }
public virtual ICollection<Note> Notes { get; set; }
[NotMapped]
public ICollection<Note> FilteredNotes
{
get
{
return Notes.Where(m => m.NoteTypeId == 8);
}
}
}
But the problem with this design is, when you select job like var job = context.Jobs.Include(x => x.Notes).FirstOrDefault(x => x.ID == jobId);, then you load all Notes to memory, then you can access filtered notes from memory like job.FilteredNotes. But when using LazyLoading it has advantage.
var job = context.Jobs.FirstOrDefault(x => x.ID == jobId);
var notes = job.FilteredNotes.ToList();
Update
You can also try Table-per-Hierarchy (TPH) mappimg. You have to create one abstract class and derived classes:
public abstract class Note
{
public int Id { get; set; }
public int NoteTypeId { get; set; }
}
public class JobNote : Note
{
}
public class OtherNote : Note
{
}
Then override OnModelCreating method:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Note>()
.Map<JobNote>(m => m.Requires("NoteTypeId").HasValue(8))
.Map<OtherNote>(m => m.Requires("NoteTypeId").HasValue(3)); // For example
}
Please note that, I do not have enough knowledge about TPH. I am just trying to show some hint. Please read further about TPH.