An extensible control design framework is utilized to declaratively define a control (both visual and non-visual) and other components. The functionality of a control may be expanded by declaratively adding behaviors and semantics via an object called an action. The control does not become unduly complex by the addition of the behaviors and semantics. The action object encapsulates well-defined functionality and is associated with an existing control. The action object is also associated with an event or trigger such that the functionality is automatically executed when the event is raised. The functionality may be packaged in an independent application component such that a user who is not familiar with programming code may easily define logic and functionality for an application in a design environment.