Lifecycle
A user sits at her browser and types in a URL. A
web page appears, with text and images and
buttons and so forth. She fills in a text box and
clicks on a button. What is going on behind the
scenes?
Every request made of the web server initiates a sequence of
steps. These steps, from beginning to end,
constitute the lifecycle of the page.
When a page is requested, it is loaded, processed, sent to the user,
and unloaded. From one end of the lifecycle to the
other, the goal of the page is to render appropriate HTML and other
output back to the requesting browser. At each
step, there are methods and events available to let you override the
default behavior or add your own programmatic enhancements.
In order to fully understand the lifecycle of the page and its
controls, it is necessary to recognize that the
Page class creates a hierarchical tree of
all the controls on the page. All the components
on the page, except for any Page directives
(described shortly), are part of this control
tree
. You can see the
control tree for any page by adding trace="true"
to the Page directive.
(Page directives are described in the next section
of this chapter. Tracing is described in detail in
Chapter 7.)
The Page itself is at the root of the tree. All
the named controls are included in the tree, referenced by control
ID. Static text, including whitespace, NewLines,
and HTML tags, are represented in the tree as
LiteralControls. The order of controls in the tree is strictly hierarchical ...
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