need help to fine tune query

HI i have this update query which works fine but just it takes about 3-4 seconds before i get the messagebox update successfully. Could you help to see what goes wrong? Is it because of the using() and the transaction rollback?

public void Update()
    {
        Syst开发者_C百科em.Data.Common.DbTransaction transaction = null;
        using (JamminDataContext db = new JamminDataContext())
        {
            try
            {
                db.Connection.Open();
                transaction = db.Connection.BeginTransaction();
                db.Transaction = transaction;

                #region Update Users
                db.Users.Attach(this, GetSingleUserById(this.Id));
                db.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, db.Users);
                db.SubmitChanges();
                #endregion

                if (this.RoleId == (int)RoleTypes.Student)
                {
                    #region Update CourseByStudents
                    foreach (CourseByStudent courseByStudent in this.courseByStudent)
                    {
                        if (courseByStudent == null) break;
                        if (courseByStudent.Id == 0)
                        {
                            courseByStudent.CourseUserStatus.UserId = this.Id;
                            db.CourseUserStatus.InsertOnSubmit(courseByStudent.CourseUserStatus);
                            db.SubmitChanges();

                            courseByStudent.StudentId = this.Id;
                            courseByStudent.CourseUserStatusId = courseByStudent.CourseUserStatus.Id;
                            db.CourseByStudents.InsertOnSubmit(courseByStudent);
                            db.SubmitChanges();
                        }
                        else
                        {
                            if(courseByStudent.CourseUserStatusCopy != courseByStudent.CourseUserStatus.Status
                                && ( courseByStudent.CourseUserStatus.Status != null
                                && courseByStudent.CourseUserStatus.Date != null))
                            {
                                //Insert to CourseUserStatus only when Status is change or add new row of course
                                courseByStudent.CourseUserStatus.UserId = this.Id;
                                db.CourseUserStatus.InsertOnSubmit(courseByStudent.CourseUserStatus);
                                db.SubmitChanges();

                                courseByStudent.CourseUserStatusId = courseByStudent.CourseUserStatus.Id;
                            }
                            courseByStudent.Update();
                        }
                    }
                    #endregion
                }

                transaction.Commit();
            }
            catch (Exception ex)
            {
                if (transaction != null) transaction.Rollback();
                Logger.Error(typeof(User), ex);
                throw;
            }
            finally
            {
                if (db.Connection.State == System.Data.ConnectionState.Open) db.Connection.Close();
            }
        }
    }

Instead of doing all the individual db.SubmitChanges() make one call to db.SubmitChanges() right before the tx.Commit(). Let me know if this improves performance. It should prevent many roundtrips to the database and thus improve the overall performance.