ASP.NET PAGE LIFE CYCLE

ASP.NET Page Life Cycle

        

A Page in an ASP.NET application consists of server controls. There  are the fundamentals building blocks of an ASP.NET application. The life cycle of an ASP.NET page, depends on whether the page is requested for the first time or it is postback. Postback is a process by which a page can request for itself.

When The Page Is Requested For The First Time 

The life cycle of a page when requested for the first time:

• Initializing : 

                                   During this phase, the server creates an instance of the server control.

• Loading : 

             During this phase, the instance of the control is loaded onto the page object in which it is   defined.

• PreRendering : 

                           During this phase, the control is loaded with the changes made to it. This prepares the controls for rendering.

• Saving : 

                          During this phase, the  state information of the control is saved. For example, if a value is set for the control during  the Load event, it is embedded in the HTML tag that will be returned to the browser.

• Rendering : 

                           During this phase, the server creates the corresponding HTML tag for the control.

• Disposing :

                           During this phase, all cleanup tasks, such as closing files and database connections opened by the control are performed.

• Unloading : 

                              During this phase, all cleanup tasks, such as destroying the instances of server control are performed. This is final event in the life cycle of server controls.

Life Cycle When The Page Processed During A Postback Event

The processing sequence in which a page is processed during a postback event is:

• Initializing : 

                                   During this phase, the server creates an instance of the server control.

• Loading View State: 

                                 During this phase, the view state of the control posted by the client is reloaded into the new instance of the control.

• Loading : 

                         During this phase, the instance of the control is loaded onto the page object in which it is defined.

• Loading The Postback Data: 

                                                    During this phase, the server searches any data corresponding to the control that is loaded in the posted by the client.

• PreRendering: 

                                       During this phase, the control is updated with the changes made to it. This prepares the controls for rendring.

•  Saving State :

                                    During this phase, the change in the state of control between the current request and the previous request of the page is saved. For each change, the corresponding event is raised. For example, if the text of a texbox is changed, the new text is saved and a text_change event is raised.

• Rendering : 

                           During this phase, the server creates the corresponding HTML tag for the control.

• Disposing :

                           During this phase, all cleanup tasks, such as closing files and database connections opened by the control are performed.

• Unloading : 

                            During this phase, all cleanup tasks, such as destroying the instances of server control are performed. This is final event in the life cycle of server controls.

The Events Associated With The Relevant Page Cycle Phases Are :

                       Page Initialization  :  Page_Init

                       View State Loading  :  LoadViewState.

                       Postback data processing  :  LoadPostData

                       Page Loading  :  Page_Load

                       PostBack Change Notification  :  Raise PostDataChangedEvent

                       PostBack Event Handing  :  RaisePostBackEvent

                       Page Pre Rendring Phase  :  Page_PreRender

                       View State Saving  :  SaveViewState

                       Page Rendring :  Page_Render

                              Page Unloading  :  Page_UnLoad