I am wondering if this is a good idea in the first place.

Basically I want to create a template upon which to build numerous sites. The idea is I can update the “core” of the website without having to change much, if at all, any application specific code.

This way, if there is a flaw in the core of one web server I can update all other webservers by simply modifying the core code.

The core code I was thinking would be a class library. Certain controller and db logic that is common to all my websites could sit in separate libraries. Each new MVC project will then reference those libraries and build on top of them.

Is this a good practice? Would it be worth the extra effort, or should I simply copy and paste the common code between projects?