private void btnAddNew_Click(object sender, EventArgs e)
        {
            AddNewStudent addStudentForm = new AddNewStudent();
            Student       student        = addStudentForm.GetNewStudent();

            if (student != null)
            {
                students.Add(student);
                StudentList.SaveStudents(students);
                FillStudentListBox();
            }
        }
        private void btnDelete_Click(object sender, EventArgs e)
        {
            int i = listStudentInfo.SelectedIndex;

            if (i != -1)
            {
                Student student = (Student)students[i];
                string  message = "Are you sure you want to delete "
                                  + student.Name + " " + student.Score + "?";
                DialogResult button = MessageBox.Show(message, "Confirm Delete",
                                                      MessageBoxButtons.YesNo);
                if (button == DialogResult.Yes)
                {
                    students.Remove(student);
                    StudentList.SaveStudents(students);
                    FillStudentListBox();
                }
            }
        }