Can I link to codebehind function on another page?

Hi All,

Many thanks in advance.  I'm pretty sure there's simple solution to this, but I can't seem to nail it down.  I have a function that I need to use throughout my website, but I don't want to have to go to every single page to update that function when there's a change.

Is there a way to save the function in one place and point each page to it?

Thanks!
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