Hi Richard,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
I am afraid, currently the feature of getting slide id is missing in the latest version of unified API of Aspose.Slides for .NET. We have already registered an issue in our issue tracking system with issue id: SLIDESNET-34978 for the implementation of this feature. I have attached this thread with the issue in issue tracking system and you will get a notification once the feature gets supported.
Thanks & Regards,