General Page Life Cycle Stages printable pdf download

General Page Life-cycle Stages

Common Life-cycle Events

Stage

Description

Page Event

Typical Use

Page request

The page request occurs before the page life cycle begins. When the page is requested by a

PreInit

Use this event for the following:

user, ASP.NET determines whether the page needs to be parsed and compiled or whether a

• Check the IsPostBack property to determine whether this is the first time the page is

cached version of the page can be sent in response without running the page.

being processed.

• Create or re-create dynamic controls.

Start

In the start step, page properties such as Request and Response are set. At this stage, the page

• Set a master page dynamically.

also determines whether the request is a postback or a new request and sets the IsPostBack

• Set the Theme property dynamically.

property. Additionally, during the start step, the page's UICulture property is set.

• Read or set profile property values.

Note: If the request is a postback, the values of the controls have not yet been restored

Page

During page initialization, controls on the page are available and each control's UniqueID

from view state. If you set a control property at this stage, its value might be overwritten

initialization

property is set. Any themes are also applied to the page. If the current request is a postback,

in the next event.

the postback data has not yet been loaded and control property values have not been restored

to the values from view state.

Init

Raised after all controls have been initialized and any skin settings have been applied. Use

this event to read or initialize control properties.

Load

During load, if the current request is a postback, control properties are loaded with information

recovered from view state and control state.

InitComplete

Raised by the Page object. Use this event for processing tasks that require all initialization

be complete.

Validation

During validation, the Validate method of all validator controls is called, which sets the IsValid

property of individual validator controls and of the page.

PreLoad

Use this event if you need to perform processing on your page or control before the Load

event. After the Page raises this event, it loads view state for itself and all controls, and

Postback event

If the request is a postback, any event handlers are called.

then processes any postback data included with the Request instance.

handling

Load

The Page calls the OnLoad event method on the Page, then recursively does the same for

Rendering

Before rendering, view state is saved for the page and all controls. During the rendering phase,

each child control, which does the same for each of its child controls until the page and all

the page calls the Render method for each control, providing a text writer that writes its output

controls are loaded.

to the OutputStream of the page's Response property.

Control events

Use these events to handle specific control events, such as a Button control's Click event or

Unload

Unload is called after the page has been fully rendered, sent to the client, and is ready to be

a TextBox control's TextChanged event. In a postback request, if the page contains

discarded. At this point, page properties such as Response and Request are unloaded and any

validator controls, check the IsValid property of the Page and of individual validation

cleanup is performed.

controls before performing any processing.

LoadComplete

Use this event for tasks that require that all other controls on the page be loaded.

Data Binding Events for Data-Bound Controls

PreRender

Before this event occurs:

• The Page object calls EnsureChildControls for each control and for the page.

Control Event

Typical Use

• Each data bound control whose DataSourceID property is set calls its DataBind

method.

DataBinding

This event is raised by data-bound controls before the PreRender event of the

• The PreRender event occurs for each control on the page. Use the event to make final

containing control (or of the Page object) and marks the beginning of binding

changes to the contents of the page or its controls.

the control to the data.

SaveStateComplete

Before this event occurs, ViewState has been saved for the page and for all controls. Any

RowCreated (GridView)

Use this event to manipulate content that is not dependent on data binding. For

changes to the page or controls at this point will be ignored. Use this event perform tasks

ItemCreated (DataList,

example, at run time, you might programmatically add formatting to a header

that require view state to be saved, but that do not make any changes to controls.

DetailsView, SiteMapPath,

or footer row in a GridView control.

DataGrid, FormView,

Render

This is not an event; instead, at this stage of processing, the Page object calls this method

Repeater)

on each control. All ASP.NET Web server controls have a Render method that writes out

the control's markup that is sent to the browser. If you create a custom control, you

RowDataBound (GridView)

When this event occurs, data is available in the row or item, so you can format

typically override this method to output the control's markup. However, if your custom

ItemDataBound (DataList,

data or set the FilterExpression property on child data source controls for

control incorporates only standard ASP.NET Web server controls and no custom markup,

SiteMapPath, DataGrid,

displaying related data within the row or item.

you do not need to override the Render method. A user control (an .ascx file) automatically

Repeater)

incorporates rendering, so you do not need to explicitly render the control in code.

DataBound

This event marks the end of data-binding operations in a data-bound control.

Unload

This event occurs for each control and then for the page. In controls, use this event to do

In a GridView control, data binding is complete for all rows and any child

final cleanup for specific controls, such as closing control-specific database connections. For

controls. Use this event to format data bound content or to initiate data binding

the page itself, use this event to do final cleanup work, such as closing open files and

in other controls that depend on values from the current control's content.

database connections, or finishing up logging or other request-specific tasks. Note: During

the unload stage, the page and its controls have been rendered, so you cannot make

further changes to the response stream. If you attempt to call a method such as the

More .NET Cheat Sheats available at

Response.Write method, the page will throw an exception.

More info at

General Page Life Cycle Stages

Related Articles

Related forms

Related Categories