Noun
code-behind (uncountable)
English Wikipedia has an article on:code-behindWikipedia
(computing, programming) A technique in object-oriented programming in which the visual and back-end source code are stored in separate files, allowing designers and programmers to work independently. Code-behind is a technique used in Microsoft programming platforms, including ASP.NET and XAML, where the practice is facilitated by separating the visual and code aspects through the use of partial classes.
This Visual Basic code, sometimes referred to as a Visual Basic code-behind file, follows the syntax rules of the Visual Basic programming language and connects the developer to the power and functionality of the Windows operating system. Source: Internet
This folder contains registration, login, and password-related markup and code-behind files. Source: Internet
Well, I haven't seen the source code yet, but in general, this works somewhat like ASP.net code-behind. Source: Internet