How to Update (Add/Modify/Delete) keys in AppSettings section of web.config at runtime

Question

I like to Update keys/Values defined in AppSettings section of Web.config at runtime. however I DO NOT want to actually save them to Web.conf

Answer 1

I know this is an old question, but I ran into the same problem and I found that Set works in the same way as Add, and does not throw an exception, so just replace Add with Set, like so:

ConfigurationManager.AppSettings.Set(item.Key, item.Value);