Use the ODP.NET 12.1 if you want a version that works with Windows 8. That's the latest version you can download from OTN.
If you use anything earlier than ODP.NET 18.104.22.168, then it's not guaranteed to work because those earlier versions are not certified for Win8.
Latest Oracle 12c client (including odp.net/asp.net stuff) doesn't work for me on my Windows 8 machine.. won't install. I have a separate thread on it in Oracle Database / Installation forums. It just dies. No useful information to tell me why...
EDIT: Link for the lazy https://forums.oracle.com/thread/2584441