I have some code from my VB.NET 1.1 days that allowed me to dynamically check if Debug was enabled in web.config. I figured why re-invent the wheel in turning on/off logging
-Edit- I'm aware this doesn't specifically answer the question, as you asked for Web.Config - which immediately suggests a web.app, and is not decided at "run-time", but it does allow a good way to check if it's debug mode.
On another note, you'd not ideally interchanged between debug and release mode on the same app.. -End edit-
How about using conditional compilation??
http://msdn.microsoft.com/en-us/library/aa691099(v=vs.71).aspx
bool isDebuggingEnabled = false
#if debug
isDebuggingEnabled = true;
#endif
That surely would make the most sense, and doesn't require any specific references?
Just make sure the DEBUG Constant is turned on in your project (See picture)
