public AttendanceViewModel(IViewContainer container, string sessionId)
        {
            Container = container;
            SessionId = sessionId;

            Provider = new CourseAttendanceProvider();
            Provider.CourseAbsenceEvent = CourseAttendanceLoadedEvent;
        }
        public AttendanceComposeViewModel(IViewContainer container, ViewModelRelationship parent,
            string sessionId)
        {
            Parent = parent;
            Container = container;
            SessionId = sessionId;

            dispatchStudentProvider = new DispatchStudentProvider();
            dispatchStudentProvider.DispatchStudentEvent += DispatchStudentLoadedEvent;

            courseAttendanceProvider = new CourseAttendanceProvider();
            courseAttendanceProvider.CourseAbsenceEvent += CourseAttendancetLoadedEvent;
        }