members available across site

Question

I'm a vb programmer by nature, and I'm trying to teach myself C#. While programming in VB, I was able to create an include file which defined some publically available constants, subroutines and functions. Anytime I wanted to access one of these members, I had the ability to place an include statement into the file I was working on, and that would insert the file with all of my pre-defined members. That way, I didn't have to cut and paste all the common info into each and every aspx file on which I was working. When I do my re-write in C#, it doesn't recognize any of the members in my include file, saying that the member doesn't exist in the defined class or namespace. Can anyone tell me how to write a function or define a constant that is accessible across multiple aspx pages within a site? I appologize ahead of time if this is a simple matter, but as I said, I'm just trying to learn the language.