using (var db = new DataContext())
            {
                db.Add(doc);
               foreach (var user in users)
                    {
                        db.Execute("INSERT INTO RF_DocUser VALUES({0},{1},{2},{3})", doc.Id, user.Id, 0, DBNull.Value);
                    }
                return db.SaveChanges();
            }
            
            
            采用db.Execute来执行SQL。可以执行多条SQL。最后采用db.SaveChanges()来提交事务。