private void deleteAttandance(string attandanceUUID) { Model.Course course = courseRef; foreach (StuList stuList in course.allStulist()) { foreach (Student stu in stuList.allStudents()) { stu.removeAttandance(attandanceUUID); } } course.removeAttandance(attandanceUUID); GlobalStation.shareInstance.librarySave(delegate() { mainGrid.Columns.Remove(mainGrid.Columns[attandanceUUID]); }, delegate() { GlobalStation.shareInstance.librarysInit(); }); }