Additional Page Life Cycle Considerations

Additional Page Life Cycle Considerations

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Individual ASP.NET server controls have their own life cycle that is similar to the page life cycle. For example, a control's Init and Load events occur during the corresponding page events.

Although both Init and Load recursively occur on each control, they happen in reverse order. The Init event (and also the Unload event) for each child control occur before the corresponding event is raised for its container (bottom-up). However the Load event for a container occurs before the Load events for its child controls (top-down).

When you create a class that inherits from the Page class, in addition to handling events raised by the page, you can override methods from the page's base class. For example, you can override the page's InitializeCulture method to dynamically set culture information. Note that when an event handler is created using the Page_event syntax, the base implementation is implicitly called and therefore you do not need to call it in your method. For example, the base page class's OnLoad method is always called, whether you create a Page_Load method or not. However, if you override the page OnLoad method with the override keyword (Overrides in Visual Basic), you must explicitly call the base method. For example, if you override the OnLoad method on the page, you must call base.Load (MyBase.Load in Visual Basic) in order for the base implementation to be run.

The following illustration shows some of the most important methods of the Page class that you can override in order to add code that executes at specific points in the page life cycle. (For a complete list of page methods and events, see the Page class.) The illustration also shows how these methods relate to page events and to control events. The sequence of methods and events in the illustration is from top to bottom, and within each row from left to right.