private void btnAddUser_Click(object sender, EventArgs e)
        {
            AppUser u = new AppUser();

            u.fullname = textBox1.Text;
            u.username = textBox2.Text;
            u.userType = checkBox1.Checked;

            try
            {
                AppUserDAO.addAppUser(u);

                MessageBox.Show("User added successfully.", "HUGO",
                                MessageBoxButtons.OK, MessageBoxIcon.Information);

                btnClearUser_Click(sender, e);

                updateAdminControls();
            }
            catch (Exception exception)
            {
                MessageBox.Show("Error: " + exception.Message, "Error dialog",
                                MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }