Hello, today I was working with a sample for a colleague and got a
problem. The sample was quite simple, with a micro cds database like:
CREATE TABLE ARTIST
(
NUM_REGISTO NUMBER PRIMARY KEY NOT NULL,
NOME VARCHAR2(200) NOT NULL,
);
CREATE TABLE ALBUM
(
NUM_REGISTO NUMBER PRIMARY KEY NOT NULL,
NUM_ARTIST REFERENCES ARTIST(NUM_REGISTO) NOT NULL,
TITULO VARCHAR2(200) NOT NULL,
);
CREATE TABLE TRACK
(
NUM_REGISTO NUMBER PRIMARY KEY NOT NULL,
NUM_ALBUM REFERENCES ALBUM(NUM_REGISTO) NOT NULL,
NOME VARCHAR2(200) NOT NULL,
DURACAO NUMBER NOT NULL
);
After creating the code with dbmetal, I was trying to add tracks to
albums. For existing albums, the following code works fine:
//----------------
Album album = (from a in database.Album
where a.Numregisto == 123
select a).SingleOrDefault();
if (album != null)
{
Track t = new Track();
t.Duracao = 10;
t.Nome = "track1";
t.Numregisto = 1;
album.Track.Add(t);
database.Track.InsertOnSubmit(t);
database.SubmitChanges();
}
//----------------
On new albums, I got confused. If I do:
//----------------
Album album = new Album();
album.Numregisto = 4444;
album.Titulo = "tttt";
album.Numartist = 1231;
Track t = new Track();
t.Numalbum = album.Numregisto;
t.Duracao = 10;
t.Nome = "track1";
database.Album.InsertOnSubmit(album);
database.Track.InsertOnSubmit(t);
database.SubmitChanges();
//----------------
everything is inserted. However, the Album.Track property (an entity
set) only gets populated after the SubmitChanges (which is not good
for UI applications where a gridview may be bound to that property)
If I manually add the track to the album tracks with
"album.Track.Add(t)" I get an InvalidOperationException ("The
EntitySet is already loaded and the source cannot be changed").
Also, does the order for InsertOnSubmit matter? I thought we could,
for example, call InsertOnSubmit for the track before the album, as
the update/insert order would be automatically calculated.
How's this typically done? I've tried so many combinations that I'm
afraid I may be missing something trivial here.
Thanks,
Pedro Ferreira
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