the current version of wordnet, is a python project and is only the database files (in yaml format) that can be converted to other formats:
https://github.com/globalwordnet/english-wordnet
here is a current open source python library:
https://github.com/goodmami/wn
here is an 20 year old implementation for C# that probably uses the old format files (I assume you are using the 20 year old windows app):