Version 0.9, source in C#
The first public version of RadixPro was written in C#. The original source is still available.
It is a full working version with the essential functionality, including Swiss Ephemeris based calculations, aspects, midpoints and chart drawing.
You can download the source right here.
Be sure also to check the following fix.
Updated version
Thanks to the work of Kelley Smoot Garrett a new version including the above mentioned fix is now available.
An English version and a dutch version.
Thanks, Kelley!