public void confirm_Login()
        {
            confirmLogin confirmLogin;

            confirmLogin = new confirmLogin(txtUserName.Text.ToString(), txtPassword.Password.ToString());
            if (confirmLogin.confirm_Login() == "admin")
            {
                confirmPerson.setPersonPermission("ADMIN");
                if (confirmFinishRegister.getConfirm() == true)
                {
                    var main = new MainWindow();
                    main.Show();
                    this.Close();
                }
                else
                {
                    var exam = new  ExamRegister();
                    exam.Show();
                    this.Close();
                }
            }
            if (confirmLogin.confirm_Login() == "user")
            {
                confirmPerson.setPersonPermission("USER");
                if (confirmFinishRegister.getConfirm() == true)
                {
                    var main = new MainWindow();
                    main.Show();
                    this.Close();
                }
                else
                {
                    var exam = new ExamRegister();
                    exam.Show();
                    this.Close();
                }
            }
            else if (confirmLogin.confirm_Login() == "none")
            {
                MessageBox.Show("Authentication failed", "Login");
            }
        }
        private void ResetRegisterPhase(object sender, RoutedEventArgs e)
        {
            var finish = MessageBox.Show("Do you want to reset Register phase?", "Alert", MessageBoxButton.YesNo);

            if (finish == MessageBoxResult.Yes)
            {
                if (confirmPerson.getPersonPermission() == "ADMIN")
                {
                    SqlConnection con = new SqlConnection(sqlConnection.CONNECTION);
                    //con.ConnectionString = ConfigurationManager.ConnectionStrings[@"Data Source=PCHIEU\SQLEXPRESS;Initial Catalog=QLTuyenSinh;Integrated Security=True"].ConnectionString;
                    con.Open();

                    SqlCommand cmd = con.CreateCommand();

                    string update = "update CONFIRM_REGISTER set confirm = 'false'";
                    cmd.CommandText = update;
                    cmd.ExecuteNonQuery();
                    MessageBox.Show("REGISTER PHASE HAS BEEN RESET.");

                    var register = new ExamRegister();
                    register.Show();
                    this.Close();
                }
                else
                {
                    var Result = MessageBox.Show("You need ADMIN permission\n Do you want to log out?", "Message", MessageBoxButton.YesNo, MessageBoxImage.Question);
                    if (Result == MessageBoxResult.Yes)
                    {
                        // click button log_out
                        confirmPerson.setPersonPermission("NONE");

                        var login = new Login();
                        login.Show();
                        this.Close();
                    }
                    else if (Result == MessageBoxResult.No)
                    {
                    }
                }
            }
        }