How to insert multiple items in Quickbook Invoice

I need to insert a new invoice for a particular customer , I can able to insert , but i don't have any idea about how to insert multiple items in invoice. How to use the property Items and ItemsElementName to insert multiple items. If my question is unclear please let me know. I have attached the snapshot and code for reference.

Code:

protected void btnsendInvoiceDetails_Click(object sender, EventArgs e)
        {
                string accessToken = "lvprdRM1HLr6o11Bnip2fGizlXWbFfADnS1Btvm2L4VPOTRI";
                string appToken = "297db54bb5526b494adb86fb2a41063192cd";
                string accessTokenSecret = "JfSTrprW83JTXrSVHD3uf7th23gP0SOzBQcn4Nrt";
                string consumerKey = "qyprdKLN5YHpCPSlWQZTiKVc28dywR";
                string consumerSecret = "JPMNB37YnCPGU9m9vuXkF2M71lbDb7blhcLB7HeF";
                string companyID = "813162085";
                OAuthRequestValidator oauthValidator = new OAuthRequestValidator(accessToken, accessTokenSecret, consumerKey, consumerSecret);
                ServiceContext context = new ServiceContext(oauthValidator,appToken,companyID, IntuitServicesType.QBO);
                DataServices service = new DataServices(context);

                InvoiceHeader a = new InvoiceHeader();
                a.CustomerName = "Antivirus Norton Security";
                a.CustomerId = new IdType { idDomain = idDomainEnum.QBO, Value = "6" };
                a.TotalAmt = 157.00m;
                a.SubTotalAmt = 37.00m;
                a.ShipMethodName = "Gmail";
                a.ShipMethodId = new IdType { idDomain = idDomainEnum.QBO, Value = "41" };
                a.DocNumber = "1040";
                a.DueDateSpecified = true;
               // a.Item = 10.00m;
               //a.ItemElementName = ItemChoiceType2.DiscountAmt;
                DateTime dt = Convert.ToDateTime("08/07/2013");
                a.DueDate = dt;

                InvoiceLine mnm = new InvoiceLine();
                mnm.Desc = "Antivirus Norton Security The Best Security ";
                mnm.Id = new IdType { idDomain = idDomainEnum.QBO, Value = "25" };
                mnm.Amount = 65.00m;
                mnm.AmountSpecified = true;
               // mnm.Items = "Europe";
               //mnm.ItemsElementName = "Zebronic";
                InvoiceLine[] invline = new InvoiceLine[] { mnm };
                var invoices = new Intuit.Ipp.Data.Qbo.Invoice();
                invoices.Header = a;
                invoices.Line = invline;
                var addedInvoice = service.Add(invoices);
                var qboInvoices = service.FindAll(invoices, 1,10);
                foreach (var qboinv in qboInvoices)
                {
                    string id = Convert.ToString(qboinv.Id.Value);
                }
                GridView1.DataSource = invoices;
                GridView1.DataBind();
        }

Image:

Try this:

InvoiceLine i = new InvoiceLine();
i.ItemsElementName = new ItemsChoiceType2[1];
i.ItemsElementName[0] = ItemsChoiceType2.ItemId;
i.Items = new Intuit.Ipp.Data.Qbd.IdType[1];
i.Items[0] = new Intuit.Ipp.Data.Qbd.IdType() { idDomain = Intuit.Ipp.Data.Qbd.idDomainEnum.QBO, Value = "6" };