FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Understanding the Page Life Cycle can be very important as you begin to build Pages with MasterPages and UserControls.

Does the Init event fire first for the Page, the MasterPage or the UserControl?
What about the Load event?

If you make an incorrect assumption about the sequence that these events fire, then you may end up with a page that simply doesn't behave the way you had anticipated.

By running a simple test, we can see exactly when each event fires. Our test setup is composed of a Page, MasterPage, UserControl, Nested UserControl and Button control as follows:

The Page is tied to the MasterPage
The UserControl is on the Page
The Nested UserControl is on the UserControl
The Button is on the Nested UserControl.
Clicking the Button calls the Page.DataBind method

Each event on these controls has been set to call Debug.WriteLine as each event is raised. In addition to the events that get raised for regular pages, I've also set up an HttpModule and wired up all of those events as well. The results in the Debug output window of running this page and Clicking the Button are as follows:

BeginRequest - HttpModule
AuthenticateRequest - HttpModule
PostAuthenticateRequest - HttpModule
PostAuthorizeRequest - HttpModule
ResolveRequestCache - HttpModule
PostResolveRequestCache - HttpModule
PostMapRequestHandler - HttpModule
AcquireRequestState - HttpModule
PostAcquireRequestState - HttpModule
PreRequestHandlerExecute - HttpModule

PreInit - Page

Init - ChildUserControl
Init - UserControl
Init - MasterPage
Init - Page

InitComplete - Page

LoadPageStateFromPersistenceMedium - Page

ProcessPostData (first try) - Page

PreLoad - Page

Load - Page
Load - MasterPage
Load - UserControl
Load - ChildUserControl

ProcessPostData (second try) - Page

RaiseChangedEvents - Page
RaisePostBackEvent - Page

Click - Button - ChildUserControl

    DataBinding - Page
    DataBinding - MasterPage
    DataBinding - UserControl
    DataBinding - ChildUserControl

LoadComplete - Page

PreRender - Page
PreRender - MasterPage
PreRender - UserControl
PreRender - ChildUserControl

PreRenderComplete - Page

SaveViewState - Page
SavePageStateToPersistenceMedium - Page
SaveStateComplete - Page

Unload - ChildUserControl
Unload - UserControl
Unload - MasterPage
Unload - Page

PostRequestHandlerExecute - HttpModule
ReleaseRequestState - HttpModule
PostReleaseRequestState - HttpModule
UpdateRequestCache - HttpModule
PostUpdateRequestCache - HttpModule
EndRequest - HttpModule
PreSendRequestHeaders - HttpModule
PreSendRequestContent - HttpModule

I hope that you will find this information useful.

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Thanks Mike,

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Thanks a lot for this post. It sure cleared some confusions. But can u please explain where this HttpModule comes into picture. Don't all the events on page, usercontrol, master page, etc, fire without even wiring up with HttpModule as well ? sorry if its a very naive question.

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

slsp
Don't all the events on page, usercontrol, master page, etc, fire without even wiring up with HttpModule as well ?

Yes - those events would fire in that same sequence even without the HttpModule.

I included the events from the HttpModule as a person developing an HttpModule might be interested to see the sequence of the HttpModule events and how they relate to the page life cycle.

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Hey Mike

I really apreciate the way u wrote the post in simple and concise manner. I have only one question are these event in 1.1 or 2.0 and what about LoadPostbackData and LoadViewStateData. Can you please explain. And can you please explain the events in the article. http://www.eggheadcafe.com/articles/20051227.asp. In 2 respect one without a postback and one with postback.

Help is highly apreciated.

Regards

Mohit Thakral

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

I have a page with some dynamically added controls. My MasterPage control-loading code is wrapped in an If Not IsPostback condition so naturally none of the load events of the child controls fire, but it appears that the critical button-click of the child controls doesn't fire either.Is that to be expected?

pamela

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

The Load events for the child controls is not affected by using If Not IsPostBack in the load event of the master page.

The more likely cause for your load events not firing and button-click events not firing has to do with your controls being dynamically added to your page. Give this faq a read to find some tips on getting your dynamic controls working: http://forums.asp.net/t/1186195.aspx

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Actually they are affected, since the child controls are dynamically loaded from the page.Load event and if they are not loaded, their Load events probably won't fire.

The link mosessaur gave me to Dynamically Loading Controls in ASP.NET is A Pain explained the problem and the solution fairly well.

Thanks for the additional info

pamela

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

the load events will fire. When controls are loaded using LoadControl, the framework will catch up their life cycle events to the page they are being loaded into. if you load them too late though, they will not fire click events and process viewstate correctly.

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Thanks for this post, it is very good for a starter like me.

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

Thanks a lot nice sequence steps about events but what about LoadPostbackData and LoadViewStateData ?

Re: FAQ: Sequence that events are raised for Pages, UserControls, MasterPages and HttpModules

I've added a few additional events to the original post for you:

<div mce_keep="true">LoadPageStateFromPersistenceMedium </div>
<div mce_keep="true">ProcessPostData (first try)</div>
<div mce_keep="true">ProcessPostData (second try)</div>
RaiseChangedEvents
RaisePostBackEvent
SaveViewState
SavePageStateToPersistenceMedium