ASP.NET Page Life Cycle Overview

Stage	Description
Page request	The page request occurs before the page life cycle begins. When the page is requested by a  user, ASP.NET determines whether the page needs to be parsed and compiled (therefore  beginning the life of a page), or whether a cached version of the page can be sent in  response without running the page.
Start	In the start stage, page properties such as Request and Response are set. At this stage, the  page also determines whether the request is a postback or a new request and sets the  IsPostBack property. The page also sets the UICulture property.
Initialization	During page initialization, controls on the page are available and each control's UniqueID  property is set. A master page and themes are also applied to the page if applicable. If the  current request is a postback, the postback data has not yet been loaded and contro l property values have not been restored to the values from view state.
Load	During load, if the current request is a postback, control properties are loaded with  information recovered from view state and control state.
Postback event handling	If the request is a postback, control event handlers are called. After that, the Validate method  of all validator controls is called, which sets the IsValid property of individual validator  controls and of the page.
Rendering	Before rendering, view state is saved for the page and all controls. During the rendering stage, the page calls the  Render method for each control, providing a text writer that writes its output to the OutputStream object of the page's Responseproperty.
Unload	The Unload event is raised after the page has been fully rendered, sent to the client, and is  ready to be discarded. At this point, page properties such as Response and Request are  unloaded and cleanup is performed.