General Page Life-Cycle Event Stages

The events occur in the following sequence.

Its best to turn on tracing(<% @Page Trace=”true”%>) and track the flow of events :

PageRequest – 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.

PreInit– This event represents the entry point of the page life cycle. If you need to change the Master page or theme programmatically, then this would be the event to do so. Dynamic controls are created in this event.

protected void Page_PreInit(object sender, EventArgs e)

Init – Each control in the control collection is initialized. i.e., During page Intialization, 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 control property values have not been restored to the values from viewstate.

protected void Page_Init(object sender, EventArgs e)

Init Complete* - Page is initialized and the process is completed.

protected void Page_InitComplete(object sender, EventArgs e)

PreLoad* - This event is called before the loading of the page is completed.

protected void Page_PreLoad(object sender, EventArgs e)

Load– This event is raised for the Page and then all child controls. The controls properties and view state and control state can be accessed at this stage. This event indicates that the controls have been fully loaded.

protected void Page_Load(object sender, EventArgs e)

LoadComplete* - This event signals indicates that the page has been loaded in the memory. It also marks the beginning of the rendering stage.

protected void Page_LoadComplete(object sender, EventArgs e)

PreRender – If you need to make any final updates to the contents of the controls or the page, then use this event. It first fires for the page and then for all the controls.

protected void Page_PreRender(object sender, EventArgs e)

Savestate

Rendering – Before rendering, viewstate is saved for the page and all controls. At this 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 Response property.

PreRenderComplete* - Is called to explicitly state that the PreRender phase is completed.

protected void Page_PreRenderComplete(object sender, EventArgs e)

SaveStateComplete* - In this event, the current state of the control is completely saved to the ViewState.

protected void Page_SaveStateComplete(object sender, EventArgs e)

Unload – This event is typically used for closing files and database connections. At times, it is also used for logging some wrap-up tasks.

protected void Page_Unload(object sender, EventArgs e)

 

The events marked with *  have been introduced in ASP.NET 2.0.



page life cycle -- click to download the document

 

Comparison with Init and Load events in Master and content pages:

Page Init Event	Page Load event
1. Execution sequence starts from Init event of Main master page--> Sub Master Page --> ……. -->Requested ASPX page init event.	1. Execution sequence starts from Load event of Requested ASPX page --> Sub Master Page --> ……. --> Main master page load event.