Answer by theodox for Reading and writing to a custom config in c#

If all you need is really simple key-value pairs (like an old .ini or .cfg file), there's also local storage from ApplicationData.Current:

ApplicationData.Current.LocalSettings.Values["test"] = "Setting Value"; string t = (string)ApplicationData.Current.LocalSettings.Values["test"]; 

However this is tied to a single application, not sure how well it would handle the multiple threads / multiple instances issue.