Where do I find the source code for the core and project modules? In particular, I'm interested in the "code behind" files for the .ascx pages and the Info and Controller classes for the modules. I don't see them in the source code downloads.

I am looking for the technique used to pass data between modules, or more specifically, to have an event raised by one module pane to cause another module pane to refresh. For example, in the Store module there is typically a list of product categories in a module pane and a list of the products in that category in another. When the user selects a new product category from the list, the product list is then refreshed with the products in the selected category. What is the preferred mechanism for doing this?