Insert in nested field - sql

Question

I'm a new user in LINQ to SQL and I have some problems using it.
I've used LINQ to SQL Designer and I have created my classes, mapped on the DB tables.
In particular, I have one class, named voice:
[global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.voce")]
public partial class voce : INotifyPropertyChanging, INotifyPropertyChanged
{
private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
private int _id_voce;
... other private fields;
private int _category;
private EntityRef<category> _category1;
public voce()
{
this._riepilogo = new EntitySet<riepilogo>(new Action<riepilogo>(this.attach_riepilogo), new Action<riepilogo>(this.detach_riepilogo));
this._hera = default(EntityRef<hera>);
this._category1 = default(EntityRef<category>);
OnCreated();
}
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_id_voce", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
public int id_voce
{
get
{
return this._id_voce;
}
set
{
if ((this._id_voce != value))
{
this.Onid_voceChanging(value);
this.SendPropertyChanging();
this._id_voce = value;
this.SendPropertyChanged("id_voce");
this.Onid_voceChanged();
}
}
}
......
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_category", DbType="Int NOT NULL")]
public int category
{
get
{
return this._category;
}
set
{
if ((this._category != value))
{
if (this._category1.HasLoadedOrAssignedValue)
{
throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException();
}
this.OncategoryChanging(value);
this.SendPropertyChanging();
this._category = value;
this.SendPropertyChanged("category");
this.OncategoryChanged();
}
}
}
As you can see, voce class has a field named category that refers to a table named category.
When I add a new voce to my database, I create a new voce istance and, using the DataContext, i simply add it, using:
voce v = new voce(){...field, category1 = //create or retrieve category};
In particular, the category field is retrieved from the DB if already exists or, if not, it is inserted, before I insert the voice.
The problem is that when I add the voice in the database:
datacontext.InsertOnSubmit(v);
datacontext.SubmitChanges();
it inserts the category again, failing with the unique contraint.
How can I add a voice without adding every nested object?
Thank you and sorry for my bad English.

Answer 1

internal category GetCategoryFromDescription (string desc, Utility.VOICE_MODALITY mode)
{
bool type = mode == Utility.VOICE_MODALITY.ENTRATA ? true : false;
var query = from cat in dc.category
where cat.description == desc && cat.type == type
select cat;
if (query.Count() == 0)
{
category newC = new category() { description = desc };
dc.category.InsertOnSubmit(newC);
dc.SubmitChanges();
return newC;
}
else
return query.Single();
}