I am moving your post to the WebEx Developer space for better visibility and access to feedback.
I hope this helps.
Moderator for Cisco Customer Communities
Here is the url for the WebEx XML API Reference Guide. You can cobble together a request from the examples in the Training Session Service section. It doesn't help if you want to create classes or anything but you can build the xml requests as strings and at least get a response back.
Some example code for the XML API has already been provided for .NET @ https://developer.cisco.com/site/webex-developer/develop-test/xml-api/sample-code/