public bool AssignCourseTeacher(CourseTeacher courseTeacher) { try { if (IsCourseTeacherPairExist(courseTeacher)) { throw new Exception("This course already assigned to this teacher."); } else { if (IsCourseAssign(courseTeacher.CourseId)) { throw new Exception("Course already assigned."); } else { CourseGetway courseGetway = new CourseGetway(); return(courseGetway.AssignCourseTeacher(courseTeacher)); } } } catch (Exception) { throw; } }