private void btnRefress_Click(object sender, EventArgs e)
        {
            Student student = new Student();

            StudentdataGridView.DataSource = StudentDB.DisplayStudents();
            txtStudentNumber.Text          = "";
            txtFirstName.Text   = "";
            txtLastName.Text    = "";
            txtPhoneNumber.Text = "";
        }
 public DataTable DisplayStudents()
 {
     return(StudentDB.DisplayStudents());
 }