yes , i got some idea from msdn about OpenWebConfiguration and OpenExeConfiguration Method,and i do some test about it  , what's happed?

when i modify something like connectionString and CustomeSection by code, it's ok when application running, even the connectionstrings is readonly( it's too many properties was readonly ),no any exception, but the value had no saved to disk. when the application was shutdown, all the value of my modified all lost.

Why?

anyone would tell me ? thks very much!!