When ASP.NET determines which HttpHandler to pass a request to, it uses something similar to a Front Controller. Front Controller is characterized by a single handler for all requests (like System.Web.UI.Page). Once the request reaches the Page class, though, the Page Controller pattern takes over.
Within the ASP.NET implementation of Page Controller, there are elements of the Model View Controller pattern. Model View Controller separates the model (business objects, data, and processes) from the view (the display of information). The controller responds to user input and updates the model and view. Roughly speaking, an ASPX page represents the View while its codebehind file represents a hybrid Model-Controller. If you were to pull all business and data-related code out of the codebehind and leave only event handling code, this would turn the codebehind into a pure Controller while the new class containing the business logic would be the Model.
