Adding Records to Two Database Tables in Single Form Page in ASP.Net

Dear All,

I a problem defining the variable @Bestilling in the codeBehind for adding the record to the database using a single form page. The database design with corresponding form are as below:

My ASPX.CS:

        private void GridView1_BindData()
        {
            SqlConnection conn = new SqlConnection(connStr);
            SqlDataAdapter dAd = new SqlDataAdapter("SELECT kart_DemoOrder.OrderID, kart_DemoBestilling.BestillingID, kart_DemoOrder.BestillingKartType1, kart_DemoOrder.BestillingKartNummer1, kart_DemoOrder.BestillingAntallKart1 FROM kart_DemoOrder INNER JOIN kart_DemoBestilling ON kart_DemoOrder.BestillingID = kart_DemoBestilling.BestillingID", conn);
            DataSet dSet = new DataSet();
            try
            {
                dAd.Fill(dSet, "PagesData");
                GridView1.DataSource = dSet.Tables["PagesData"].DefaultView;
                GridView1.DataBind();
            }
            catch (Exception ee)
            {
               // lblMessage.Text = ee.Message.ToString();
            }
            finally
            {
                dSet.Dispose();
                dAd.Dispose();
                conn.Close();
                conn.Dispose();
            }
        }
        
        protected void GridView1_AddNewRecord(String BestillerReferanse, String BestillerNavn, bool isUpdate)
        {
            SqlConnection connection = new SqlConnection(GetConnectionString());
            string query1 = string.Empty;

            if (!isUpdate)
            {
                query1 = "INSERT INTO kart_DemoBestilling" +
                    "(BestillerReferanse, BestillerNavn)" +
                    "VALUES (@BestillerReferanse, @BestillerNavn)";
            }
            else
            {
                query1 = "UPDATE kart_DemoBestilling" +
                    "SET BestillerReferanse = @BestillerReferanse, BestillerNavn = @BestillerNavn" +
                    "WHERE BestillingID = @BestillingID";
            }
            try
            {
                connection.Open();
                SqlCommand cmd = new SqlCommand(query1, connection);

                cmd.Parameters.AddWithValue("@BestillerReferanse", BestillerReferanse);
                cmd.Parameters.AddWithValue("@BestillerNavn", BestillerNavn);

                cmd.CommandType = CommandType.Text;
                cmd.ExecuteNonQuery();
            }
            catch (Exception ee)
            {
                // lblMessage.Text = ee.Message.ToString();
            }
        }
        
                protected void GridView1_AddNewRecord(object sender, EventArgs e)
        {
            string constr = ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString;
            SqlConnection con = new SqlConnection(constr);

            string query2 = "INSERT INTO kart_DemoOrder(BestillingID, BestillingKartType1, BestillingKartNummer1, BestillingAntallKart1) VALUES(@BestillingID, @BestillingKartType1, @BestillingKartNummer1, @BestillingAntallKart1)";

            int rowIndex = 0;

            if (ViewState["CurrentTable"] != null)
            {
                DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];

                if (dtCurrentTable.Rows.Count > 0)
                {
                    for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
                    {
                            // 111111111111111111111111111111111111111111111111111111111111111111111111111111

                            DropDownList ddBestillingKartType1 = (DropDownList)Gridview2.Rows[rowIndex].Cells[1].FindControl("dropDownBestillingKartType1");
                            DropDownList ddBestillingKartNummer1 = (DropDownList)Gridview2.Rows[rowIndex].Cells[2].FindControl("dropDownBestillingKartNummer1");
                            TextBox tBestillingAntallKart1 = (TextBox)Gridview2.Rows[rowIndex].Cells[3].FindControl("txtBestillingAntallKart1");
                            // 111111111111111111111111111111111111111111111111111111111111111111111111111111

                        con.Open();

                        SqlCommand cmd = new SqlCommand(query2);
                        cmd.Connection = con;

                        cmd.Parameters.AddWithValue("@BestillingKartType1", ddBestillingKartType1.SelectedValue);
                        cmd.Parameters.AddWithValue("@BestillingKartNummer1", ddBestillingKartNummer1.SelectedValue);
                        cmd.Parameters.AddWithValue("@BestillingAntallKart1", tBestillingAntallKart1.Text.Trim());

                        cmd.ExecuteNonQuery();
                        con.Close();
                        rowIndex++;
                    }
                }
            }
            GridView1_AddNewRecord(txtBestillerReferanse.Text, txtBestillerNavn.Text, false);
            GridView1_BindData();
        }

I get error in the method: "GridView1_AddNewRecord".

Must declare the scalar variable "@BestillingID".

Is there a way to use only one Add Method and not two as I did?

Thank you in advance