An simple Seq App example, currently under development.
The app is configured with the name of an event property. Whenever the app sees a new value for the property, it raises an event with both the new value and the list of all values seen so far.
Property values are stored in a text file under the app's storage folder, so they survive server restarts. The text file is rewritten every time a new value is seen; no provisions are made to avoid corruption in case of IO failures etc.