private void DoProwadzacych(object sender, RoutedEventArgs e)
        {
            SelectionMenuLecturer SelectionMenuLecturer_window = new SelectionMenuLecturer();

            this.Visibility = Visibility.Hidden;
            SelectionMenuLecturer_window.Show();
        }
        private void OpenWindow(object sender, RoutedEventArgs e)
        {
            /*SelectionMenuAdmin objSMA = new SelectionMenuAdmin();
             * this.Visibility = Visibility.Hidden;
             * objSMA.Show();
             */

            log_t = login_text.Text;
            if (login_text.Text == "" || password_text.Password == "")
            {
                MessageBox.Show("Uzupełnij pola login oraz hasło!", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
            }
            else
            {
                string role;
                int    id;

                bool access = Login.login(login_text.Text, password_text.Password, out role, out id);
                role = role.Trim(' ');
                if (access)
                {
                    if (role == "admin")
                    {
                        SelectionMenuAdmin admin_window = new SelectionMenuAdmin();
                        admin_window.Show();
                    }
                    else if (role == "student")
                    {
                        Student stu = MenuStudentLogic.getStudentInfo(id);
                        SelectionMenuStudent student_window = new SelectionMenuStudent(stu);
                        student_window.Show();
                    }
                    else if (role == "lecturer")
                    {
                        Lecturer lectu = MenuLecturerLogic.getLectuterData(id);
                        // MessageBox.Show(lectu.Surname);
                        SelectionMenuLecturer lecturer_window = new SelectionMenuLecturer(lectu);
                        lecturer_window.Show();
                    }
                    else
                    {
                        MessageBox.Show("Samfing is not yes!");
                    }
                }
                else
                {
                    MessageBox.Show("Błędne dane logowania!");
                }
            }
        }