Shared functions accessing page elements

I am working on a project where there are 4 nearly identicle pages.


For example, they all have a text box called "NoteList" and in every case, "NoteList" is updated with the same function with the exception of a couple words. How can I put that function someplace so that all the pages can access it?


I created a class in the App_Code folder, but I can't access page elements from within that class.


For exmple, in my code behind I might have NoteList.Text = "blah"; But I want to move that into a class so that any page with NoteList can use the function. But when I do that, it says that The name 'NoteList' does not exist in the current context.


I would just pass NoteList to the function in the class, but some of the function access a lot of elements on the page, and  I would really rather just pass 1 thing instead of having to pass every element that needs to be use ...