The commercial .NET library Aspose.iCal does the job
http://www.aspose.com/community/blogs/salman.sarfraz/archive/2008/11/21/where-is-aspose-icalendar.aspx (used to be http://www.aspose.com/categories/file-format-components/aspose.network-for-.net/default.aspx)
Or this open source parser (didn't try it)
http://sourceforge.net/projects/icalparser/
And this online iCal validator comes in handy
http://severinghaus.org/projects/icv/
Regards,
tamberg