How do I check if a Work Order has unallocated components

[indikad]

What is the best way to determine whether a Work Order still has unallocated component allocations?


I am trying to do this check on the save_start of Work Order window.

Is there already a WorkOrder property/method that indicates allocations are incomplete?
Should I be checking Stages, InputItems, OutputItems, LineDetails, or some other collection?
Which property indicates that an allocation is still outstanding/unallocated?

A small code example would be greatly appreciated.
Thanks.