code-behind files allow for a cleaner system implementation. Code-behind files allow a developer to separate the UI display from the UI processing. The only code that should exist in the ASPX file itself is code (typically script) that specifically services the display. It’s easier (although still not simple) to reuse code in a code-behind file than in a single file with inline code. It’s also possible to separate the design and development functions by allowing designers to work on the ASPX file and coders to do the code-behind development. This is much more difficult to accomplish with inline code.