private void DisplayUpdateForm()
        {
            Student selectedStu = lstStudents.SelectedItem as Student;
            var     updateForm  = new FrmAddUpdateStudent(selectedStu);

            updateForm.ShowDialog();
        }
        private void BtnAddStudent_Click(object sender, EventArgs e)
        {
            FrmAddUpdateStudent addStuForm = new FrmAddUpdateStudent();

            addStuForm.ShowDialog();
            PopulateStudentListBox();
        }