private void listView1_DoubleClick(object sender, EventArgs e)
        {
            string indexUser = listView1.SelectedItems[0].Text;

            User utilizadorAlterar = context.UserSet.Where(i => i.Username == indexUser).FirstOrDefault();

            ProjectoESGPS.Properties.Settings.Default.UserAlterar = utilizadorAlterar.Username;
            ProjectoESGPS.Properties.Settings.Default.Save();

            AddUser addUser = new AddUser();

            addUser.Show();
            this.Hide();
        }