With asp .net core we have another concept of website.
There is not a scripting language with an interpreter, but we have a software that is listening on a port.
This mean that, the code in Program.cs and Startup.cs files will be executed just the fist time, at program launch. In fact, the Startup.cs file contains the Startup class, that built the middleware pipeline and it will be executed at any request.
So, a big problem that we can have with a config file is this: to any request, we need to read it from the disk, and this can be very expansive with an huge number of users.
A first way to fix this is to use AddJsonFile in the Program class when you build the configuration, and to use like explained here.
However, I use another way to do this, because I prefer access data via dot notation.
Lets see the alternative way to use a config file.