Question

Is it possible to SubmitChanges and ignore deletes that cause Foreign Key constraint errors?

Say I have object A and B. B’s Primary Key is a Foreign Key in A. Now I change a record A in which I replace B for another B and delete the original B. An error will occur when the deleted B is referenced in another record A (or other tables containing B as Foreign Key). Is it possible to ignore the error and let the changes be made in the database, without deleting the old B?

A rec_a = (from a in db.As where a.id == some_id).First();
B rec_b_old = rec_a.B;
rec_a.B = null;
db.Bs.DeleteOnSubmit(rec_b_old);
rec_a.B = some_other_b;
db.SubmitChanges();

Answer 1

Make two calls to SubmitChanges():

A rec_a = (from a in db.As where a.id == some_id).First();
B rec_b_old = rec_a.B;
rec_a.B = null;
rec_a.B = some_other_b;
db.SubmitChanges();
db.Bs.DeleteOnSubmit(rec_b_old);
try
{
    db.SubmitChanges();
}
catch(SqlException) { } // Ignore failed delete.

The second one might fail and in that case just ignore it. It is possible to try to submit everything, dig out the failing update/delete, remove it from the pending list and retry. However it requires far more code so I don’t think it’s worth to do it here.

Another solution is to put a trigger on the A table that deletes the B record if it is orphaned.