private void btnDeleteUser_Click(object sender, EventArgs e)
 {
     try
     {
         AppUserDAO.removeAppUser(comboBox1.Text);
         MessageBox.Show("User deleted successfully.", "HUGO",
                         MessageBoxButtons.OK, MessageBoxIcon.Information);
         updateAdminControls();
     }
     catch (Exception exception)
     {
         MessageBox.Show("Error: " + exception.Message, "Error dialog",
                         MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
 }