How to fetch the note identifier from drag'n drop data

I need to create an external program that enables users to drag and drop notes e-mail documents from notes 6.5 client into it.I managed to get the ‘IStream’ from the drop data, but I don’t know the format of it.

I am sure the note’s ID or unique identifier is somewhere in the stream, but I can’t find any documentation about it.

Can someone help here?