Custom and User controls make up many of the components in the framework. User controls let programmers develop a capability once then use it in many places. Controls neatly encapsulate functions so they can be used and reused easily and safely. Reuse is the hallmark of an object oriented system, and the Dot Net framework is nothing if not object oriented.

The framework makes extensive use of User Controls to encapsulate functions. This causes a couple of problems that must be solved by using code behind to declare each control as a class. Once a control has an associated class (object) then other code can reference the class and its properties.

Class properties are a strange bird in ASP.Net. They use the Set and Get keywords and are declared in the class header. These properties are accessible to the outside world and the Set and Get code controls how they are updated and displayed.

Delegation and event bubbling are used as necessary to let subordinate controls interact with their parents.