public MainViewModel()
        {
            instance          = this;
            Courses           = new CoursesViewModel();
            CourseInstructors = new CourseInstructorsViewModel();
            Departments       = new DepartmentsViewModel();
            Students          = new StudentsViewModel();
            Instructors       = new InstructorsViewModel();
            Enrollments       = new EnrollmentsViewModel();
            OfficeAssignments = new OfficeAssignmentsViewModel();
            CreateCourse      = new CreateCourseViewModel();
            CreateStudent     = new CreateStudentViewModel();
            CreateInstructor  = new CreateInstructorViewModel();
            Login             = new LoginViewModel();
            Home = new HomeViewModel();

            CreateCourseCommand     = new Command(async() => await GoToCreateCourse());
            CreateInstructorCommand = new Command(async() => await GoToCreateInstructor());
            CreateStudentCommand    = new Command(async() => await GoToCreateStudent());
        }
        public MainViewModel()
        {
            instance = this;

            Students          = new StudentsViewModel();
            Instructors       = new InstructorsViewModel();
            Courses           = new CoursesViewModel();
            CourseInstructors = new CourseInstructorsViewModel();

            Login = new LoginViewModel();
            Home  = new HomeViewModel();

            CreateCourse     = new CreateCourseViewModel();
            CreateStudent    = new CreateStudentViewModel();
            CreateInstructor = new CreateInstructorViewModel();

            //Movies = new MoviesViewModel();

            CreateCourseCommand     = new Command(async() => await GoToCreateCourse());
            CreateInstructorCommand = new Command(async() => await GoToCreateInstructor());
            CreateStudentCommand    = new Command(async() => await GoToCreateStudent());
        }