ASP.Net User activity tracking in database

This is about a simple yet efficient activity logging framework that I want to integrate with my existing ASP.Net based web-app (I’ve a LINQ-to-SQL based SQL DB as backend). I’m using something like a service-architecture to perform DB operations – that is invoke relevant LINQ operations. I’ve a service class for almost every entity (i.e. DB table) and it handles the CRUD operations.