always on availability group

I could be wrong, but i don't think the .net application has anything to do with the availability group. That would have to do with your SQL server configuration and the environment that it's installed on. I can't find anything that says you need to do something special on the application side to work with it, SQL Server should manage this feature itself.

As Trevor mentioned, it's not a specific Kentico "thing", it's a configuration of the SQL Server and the website knowing where to connect to. Typically there would be a DNS name on a load balancer that would handle the pointers to the sql server and everything behind the name would be configuration on SQL.