why page load is called when an updatepanel is updated

Hi,

i have just observed that when a request is posted to server inside an updatepanel. then load method of page is called.

create a page with script manager and updatepanel. put a button inside the panel. add a msgbox in the load eventhandler of page.

now when u will click the button page load eventhandler would be executed. i was expecting that only the load event of update panel would be executed not the page one. because what ajax says is that whole page is not reloaded only the updatepanel is reloaded. does it mean that the ajax only helps to not activate the back button on browser but underlying it reloads the page in fact.

thanks

Hi i think you misunderstood something. what AJAX meant for is not exactly for asynchronous postbacks. This means that you cant execute two threads parallelly. But what it does is partial rendering. During an async postback all the usual events will be executed but only the contents inside the Update panel will be rendered.

hello.

well, what they're trying to say is that only the updatepanel contents will be updated during a partial postback. you can use the scriptmanager isinasyncpostback property to see if you're in a partial postback scenario:

http://asp.net/AJAX/Documentation/Live/mref/P_System_Web_UI_ScriptManager_IsInAsyncPostBack.aspx

rex_alias:

Hi i think you misunderstood something. what AJAX meant for is not exactly for asynchronous postbacks. This means that you cant execute two threads parallelly. But what it does is partial rendering. During an async postback all the usual events will be executed but only the contents inside the Update panel will be rendered.

I'm pretty sure that's exactly what AJAX is meant for.

And you can execute two threads parallelly.

Partial rendering isn't related to AJAX, you can have partial rendering without AJAX, and you can have AJAX without partial rendering, although it's implemented in the UpdatePanel and its implementation uses AJAX.

And yes, the whole life cycle of the page happens on the server, but only the relevant portions of the output are rendered into a xml based diff-gram, and sent to the client.

This is the nature of Update Panel. You can filter out the Regular Post Back with an Async by Checking the Page ScriptManager.IsInAsyncPostBack. Or if you do not want to page to be called then use the Client Centric Development Model which is calling the Web Service or Static Page Methods.