how to compare an IDispatch pointer to 'NULL'?

[RAVDM]

how to express this 'NULL'?

[Norbert_B]

'NULL', 'NIL', 'Nothing' refer all to the same value: 0.
It is a typedef to show on one look that you pass an invalid or "null"-value.

Norbert B.

[Norbert_B]

To add some significant info on this issue (forgot that you are obviously work with LabVIEW....):
There is a "Not a RefNum"-constant in the File I/O -> File Constants - palette. You could give that a try.

hope this helps,
Norbert