I want my app.config (or my web.config for that matter) to read from an SQL database instead of an XML file. How can I do that?
You can't. The .NET configuration system is only file based. Anyway, how would your program know how to connect to the database ? Of course, you can put some settings in the database, but you program will still need a config file to get the DB connection string (unless you hard-code it, which is of course not recommended)