time, populate their properties with view-state data and run control behavior code.
Following are the different stages of an ASP.NET page:
Page request - When ASP.NET gets a page request, it decides whether to parse and compile
the page, or there would be a cached version of the page; accordingly the response is sent.
Starting of page life cycle - At this stage, the Request and Response objects are set. If the
request is an old request or post back, the IsPostBack property of the page is set to true. The
UICulture property of the page is also set.
Page initialization - At this stage, the controls on the page are assigned unique ID by
setting the UniqueID property and the themes are applied. For a new request, postback data
is loaded and the control properties are restored to the view-state values.
Page load - At this stage, control properties are set using the view state and control state
values.
Validation - Validate method of the validation control is called and on its successful
execution, the IsValid property of the page is set to true.
Postback event handling - If the request is a postback oldrequest, the related event handler
is invoked.
Page rendering - At this stage, view state for the page and all controls are saved. The page
calls the Render method for each control and the output of rendering is written to the
OutputStream class of the Response property of page.
Unload - The rendered page is sent to the client and page properties, such as Response and
Request, are unloaded and all cleanup done.
ASP.NET Page Life Cycle Events
At each stage of the page life cycle, the page raises some events, which could be coded. An event
handler is basically a function or subroutine, bound to the event, using declarative attributes such
as Onclick or handle.
Following are the page life cycle events:
PreInit - PreInit is the first event in page life cycle. It checks the IsPostBack property and
determines whether the page is a postback. It sets the themes and master pages, creates
dynamic controls, and gets and sets profile property values. This event can be handled by
overloading the OnPreInit method or creating a Page_PreInit handler.
Init - Init event initializes the control property and the control tree is built. This event can be
handled by overloading the OnInit method or creating a Page_Init handler.
InitComplete - InitComplete event allows tracking of view state. All the controls turn on
view-state tracking.
LoadViewState - LoadViewState event allows loading view state information into the
controls.
LoadPostData - During this phase, the contents of all the input fields are defined with the
<form> tag are processed.
PreLoad - PreLoad occurs before the post back data is loaded in the controls. This event can
be handled by overloading the OnPreLoad method or creating a Page_PreLoad handler.
Load - The Load event is raised for the page first and then recursively for all child controls.
The controls in the control tree are created. This event can be handled by overloading the
OnLoad method or creating a Page_Load handler.
LoadComplete - The loading process is completed, control event handlers are run, and
page validation takes place. This event can be handled by overloading the OnLoadComplete
method or creating a Page_LoadComplete handler