Having recently been down this road myself, I can only suggest that you wont find the answer through searching the net. If you are connecting to an ASE server, then you have a customer technical contact. Use that person, asking them to download the earlier mentioned Sybase 15 #ESD10.
From my experience (which I freely admit, was a bad one);
Sybase makes this sort of developer resource available to paying customers only.
The download, once you have it, will include a whole bunch of extras that you wont need. I still think that PowerDesigner is a great utility, but I think that what is included is a trial version, of limited long term value. I believe that what you want from the set is the OpenClient install, selecting the ADO.NET features.
I found the whole experience, from acquiring the developer resources (just identifying the right download was a struggle), to isolating out the two files necessary from the hundreds of installed files, to the fact that the install broke my existing RapidSql and DbArtisan installs, and finally that the current version goes no further than ADO.NET 2 provider support (you wont get EF wiring for example), to be truly frustrating.
No surprise then that I have not been able to find much support for ASE using nHibernate or subsonic either.