C# as a scripting language, WebForms with no code behind, no use of app_code, a single common page inheritance for errors and the use of external include files for calling external (from the page) methods - how to debug.
a.) Remove tag referring to .\SSCode\xx.cs
b.) Take contents (functions) of xx.cs and create a file in App_Code with the calling page's name and a class wrapper with the file name
c.) In xx.aspx change the page directive references to the new class and file name.