Umm... am I missing something obvious? I can add x_line_item hidden fields to the submission and the ordered items appear in the email which is sent to the customer.
There is no mention of what has been ordered in the email sent to the merchant though? How is the merchant to know what was ordered?!
I can create a custom email, but that sort of defeats the purpose - is there no way of adding order details to the merchant email? and if not, why on earth not?
Line item data is passed to Authorize.Net from the merchant server so it is assumed that the merchant already has this data and as such it is not returned with the transaction response or displayed on merchant transaction receipts. If you would like, you can include merchant defined field data to have data to have data returned to you that you are not storing, but are collecting from the customer, prior to the submission to Authorize.net however merchant defined field data is only echoed back with the transaction response and displayed on the merchant transaction receipt and will not be displayed in the transaction details in your Authorize.Net account so please do not use them instead of line item field data unless you don't need the data to be stored in Authorize.Net.
For ASP it would look something like this:
StringBuilder sbAuthorizeItems = new StringBuilder();
foreach (rowItem in Rows)
HtmlInputHidden HI = new HtmlInputHidden();
HI.Name = "mdf_line_item";
HI.ID = "mdf_line_item";
rowItem.Cost + rowItem.AddCost,
HI.Value = sbAuthorizeItems.ToString();
sbAuthorizeItems.Length = 0;