Code Behind is a somewhat vague term that means different things to different people. I believe it was originally coined by Microsoft to describe any strategy for separating logic from content in ASP pages. Using this broad definition it could be argued that the Supervising Presenter, Presentation Model and even the View Helper are all examples of the technique. So this interpretation of code-behind lacks the sort of precision we require to discuss it as a pattern.
However, one of the most common methods for achieving code-behind in ASP and .NET uses inheritance: Presentation logic is extracted out of the view class, and into the view’s superclass. The technique has been brought over to the Flex world and is arguably one of the most talked-about and advocated presentation patterns. It is this "code-behind pattern" that I am going to look at today.