Combox对SQL中的两个字段进行多级查询应该怎么办啊？


private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox1.SelectedIndex>-1)
            {
                DataRowView drv = (DataRowView)comboBox1.SelectedItem;
                int id = Convert.ToInt32(drv.Row["departmentId"].ToString());
                using(SqlConnection conn = new SqlConnection(""))
                 {
                con.Open();
                SqlCommand cmd = new SqlCommand("seleselect * from highFireForestry where Id='" + id + "'", conn);
                SqlDataAdapter sda = new SqlDataAdapter(cmd);             
                DataTable dt = new DataTable();
                sda.Fill(dt);
                comboBox2.DataSource = dt;
                comboBox2.DisplayMember = "id";
                comboBox2.ValueMember = "name";}
            }
        }