public bool chkOverlap(Classroom classroom)
        {
            bool overlap = false;

            //find classroom and check if there is overlap
            var chkClassroom = _classroomRepository.Query().Where(x => x.ClassroomName == classroom.ClassroomName);

            if (chkClassroom != null)
            {
                foreach (var item in chkClassroom)
                {
                    if (classroom.StartDate == item.StartDate)
                    {
                        overlap = classroom.StartTime < item.EndTime && item.StartTime < classroom.EndTime;
                        if (overlap)
                        {
                            break;
                        }
                    }
                }
            }

            //find course and check overlap
            var chkCourse = _classroomRepository.Query().Where(x => x.CourseId == classroom.SelectedCourse);

            if (chkCourse != null)
            {
                foreach (var item in chkCourse)
                {
                    if (classroom.StartDate == item.StartDate)
                    {
                        overlap = classroom.StartTime < item.EndTime && item.StartTime < classroom.EndTime;
                        if (overlap)
                        {
                            break;
                        }
                    }
                }
            }
            return(overlap);
        }