Linqtosql Transaction İşlemi

Product prod = q.Single(p => p.ProductId == 15);

if (prod.UnitsInStock > 0)
   prod.UnitsInStock--;

db.Transaction = db.Connection.BeginTransaction();
try {
   db.SubmitChanges();
   db.Transaction.Commit();
}
catch {
   db.Transaction.Rollback();
   throw;
}
finally {
   db.Transaction = null;
}