We had an interesting discussion at work yesterday: for a REST api, what HTTP status code to return when a resource does not exist - a 200 OK with an empty result, a 204 NO CONTENT or a 404 NOT FOUND ?
A Lambda Expression is merely an anonymous function - a language construct. Giving a lambda a name makes it a named function.
Many web applications these days use UUIDs as primary keys in their database. While this approach has its pros and cons (see Primary Keys vs GUIDs), one of the principal advantages is that you can generate these ids outside of the database.