SOS Visual studio

            // Remplissage de combo NIVEAU
            SqlParameter ZZ = new SqlParameter("@ZZ", int.Parse(Program.levelchosen.ToString()));
            SqlCommand cmd = new SqlCommand("select nom from niveau where id_etape=@ZZ", Program.con);

            Program.con.Open();
            cmd.Parameters.Add(ZZ);
            SqlDataReader dr = cmd.ExecuteReader();
            while (dr.Read() == true)
            {
                comboBox1.Items.Add(dr.GetValue(0).ToString());
            } dr.Close(); Program.con.Close();



            // Remplissage de combo classe
            
                SqlParameter p = new SqlParameter("@p", comboBox1.SelectedItem.ToString());
                SqlCommand cmd1 = new SqlCommand("select classe .id  from classe join niveau on classe .id_Niveau =niveau .id where niveau.nom =@p", Program.con);
                Program.con.Open();
                cmd1.Parameters.Add(p);
                SqlDataReader dr1 = cmd1.ExecuteReader();
                while (dr1.Read() == true)
                {
                    comboBox2.Items.Add(dr1.GetValue(0).ToString());
                } dr1.Close(); Program.con.Close();