There's no guarantee they'll be unique. Thing about this: you can create more objects than there are int values, in which case you'd have to have duplicate hash codes. But there's a good chance that they will be distinct.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: hash codes for classes that do not implement the hashCode() method