string cs = "datasource=localhost;port=3306;database=stock;username=root;password=;";

            MySqlConnection con = new MySqlConnection(cs);
            con.Open();

            string query = "select sum(quantite) from produits; ";
            MySqlCommand cmd = new MySqlCommand(query, con);
            MySqlDataReader dr = cmd.ExecuteReader();

            if (dr.Read())
            {
                t_nbr.Text = dr.ToString();
            }
            else
            {
                MessageBox.Show("non trouvé");
            dr.Close();