ASP.Net Page Life Cycle

Understanding the Pagelife cycle is important to develop ASP.Net application.

The general Page Life Cycle Stages are:
1. Page request - Here Page is requested by the user.
2. Start – Sets the properties such as Request, Response, IsPostBack and UICulture.
3. Page initialization - Controls on the page are available and each control's UniqueID property is set.
4. Load – Controls are loaded here if it is a PostBack request.
5. Validation – Sets the IsValid property.
6. Postback Event handling – Event handlers will be called if it is PostBack.
6. Rendering - the page calls the Render method for each control, providing a text writer that writes its output to the OutputStream of the page's Response property.
7. Unload - Unload is called after the page has been fully rendered, sent to the client, and is ready to be discarded.

Common life cycle Events:
1. PreInit – Start event of the Page life cycle and here every page controls are initialized.
2. Init – This is used to read or initialize control properties.
3. InitComplete – Used for processing tasks that require all initialization be complete.
4. PreLoad - This is used before Perform any processing that should occur before Load.
5. Load - Use the OnLoad event method to set properties in controls and establish database connections.
6. Control Event - These are control specific events such as – Button Click, DropDownIndexChanged etc.
7. Load Complete - This event is used for performing those tasks which require load has been completed.
8. PreRender - In this event page insures that all child controls are created.
9. SaveStateComplete - This event occurs after viewstate encoded and saved for the page and for all controls.
10. Render – This is not an event. The page instance calls this method to output the control’s markup, after this event any changes to the page or controls are ignored.
11. Unload – Nothing but cleanup task like closing the files, database connections etc.,

This table shows stages and corresponding Events

Stage Events/Method
Initialization of the page Page_Init
Loading of the View State LoadViewState
processing of the Post back data LoadPostData
Loading of Page Page_Load
Notification of PostBack RaisePostDataChangedEvent
Handling of PostBack Event RaisePostBackEvent
Pre Rendering of Page Page_PreRender
Saving of view state SaveViewState
Rendering of Page Page_Render
Unloading of the Page Page_UnLoad