private Task <string> CreateInvoicesDoc() { InvoicesDoc invoicesDoc = new InvoicesDoc(); invoicesDoc.invoice = new AadeBookInvoiceType[2]; invoicesDoc.invoice[0] = new AadeBookInvoiceType { invoiceHeader = new InvoiceHeaderType { series = "ΑΠΥ", aa = "0005", issueDate = DateTime.Now, invoiceType = InvoiceType.Item11, currency = CurrencyType.EUR, currencySpecified = true }, issuer = new PartyType { vatNumber = "104702679", country = CountryType.GR, branch = 0 }, counterpart = new PartyType { vatNumber = "122675042", country = CountryType.GR, branch = 0 }, paymentMethods = new PaymentMethodDetailType[] { new PaymentMethodDetailType { type = 3, amount = 124 } }, invoiceDetails = new InvoiceRowType[] { new InvoiceRowType { lineNumber = 1, netValue = 100, vatCategory = 1, vatAmount = 24, incomeClassification = new IncomeClassificationType[] { new IncomeClassificationType { classificationType = IncomeClassificationValueType.E3_561_007, classificationCategory = IncomeClassificationCategoryType.category1_3, amount = 100 } } } }, invoiceSummary = new InvoiceSummaryType { totalNetValue = 100, totalVatAmount = 24, totalWithheldAmount = 0, totalFeesAmount = 0, totalStampDutyAmount = 0, totalOtherTaxesAmount = 0, totalDeductionsAmount = 0, totalGrossValue = 124, incomeClassification = new IncomeClassificationType[] { new IncomeClassificationType { classificationType = IncomeClassificationValueType.E3_561_007, classificationCategory = IncomeClassificationCategoryType.category1_3, amount = 100 } } } }; invoicesDoc.invoice[1] = new AadeBookInvoiceType { invoiceHeader = new InvoiceHeaderType { series = "ΑΠΥ", aa = "0006", issueDate = DateTime.Now, invoiceType = InvoiceType.Item11, currency = CurrencyType.EUR, currencySpecified = true }, issuer = new PartyType { vatNumber = "104702679", country = CountryType.GR, branch = 0 }, counterpart = new PartyType { vatNumber = "122675042", country = CountryType.GR, branch = 0 }, paymentMethods = new PaymentMethodDetailType[] { new PaymentMethodDetailType { type = 3, amount = 124 } }, invoiceDetails = new InvoiceRowType[] { new InvoiceRowType { lineNumber = 1, netValue = 100, vatCategory = 1, vatAmount = 24, incomeClassification = new IncomeClassificationType[] { new IncomeClassificationType { classificationType = IncomeClassificationValueType.E3_561_007, classificationCategory = IncomeClassificationCategoryType.category1_3, amount = 100 } } } }, invoiceSummary = new InvoiceSummaryType { totalNetValue = 100, totalVatAmount = 24, totalWithheldAmount = 0, totalFeesAmount = 0, totalStampDutyAmount = 0, totalOtherTaxesAmount = 0, totalDeductionsAmount = 0, totalGrossValue = 124, incomeClassification = new IncomeClassificationType[] { new IncomeClassificationType { classificationType = IncomeClassificationValueType.E3_561_007, classificationCategory = IncomeClassificationCategoryType.category1_3, amount = 100 } } } }; XmlSerializer serializer = new XmlSerializer(typeof(InvoicesDoc)); MemoryStream stream = new MemoryStream(); serializer.Serialize(stream, invoicesDoc); stream.Position = 0; StreamReader reader = new StreamReader(stream); return(reader.ReadToEndAsync()); }