Service Mapping attribute in the FulfillLine entity is having null value

Summary:

Hi

I have a requirement to create a freight charge for a line for the very first shipment if the line has backorder. To achieve this, I am try to write a logic using Service mapping algorithm in this way

if(FLineRow.FulfillLineNumber == 1)

{

FreightRow.LineType = "LINE";

FreightRow.InventoryItemId = '300000014437955';

}

But I am getting a null value for the FulfillLineNumber. Is there a way to get the FulfillLineNumber?

Regards

Ramathilagam