Which of the following controls enables AJAX functionality in ASP.NET and registers the script for the
Microsoft AJAX Library with the page?
A.
UpdateProgress
B.
UpdatePanel
C.
ScriptManager
D.
Timer
Explanation:
The ScriptManager control is used to enable AJAX functionality in ASP.NET. It handles all ASP.NET
AJAX resources on a page. This includes downloading Microsoft AJAX Library scripts to the browser
and managing partial-page updates enabled by using UpdatePanel. By default, ScriptManager is used
to register the script for the Microsoft AJAX Library with the page.
Answer B is incorrect. The UpdatePanel control is a server control that enables a user to define
areas of a page that should postback to the server without refreshing the whole page. This is known
as partial-page update. This process is organized by the ScriptManager server control and the client
PageRequestManager class. The partial-page updates are enabled by default, as the default value of
the EnablePartialRendering property of the ScriptManager control is true. The controls postback to
the server asynchronously when the partial-page updates are enabled.
Answer A is incorrect. The UpdateProgress control is used to provide status information of a partialpage update in the form of graphics or text. Multiple UpdateProgress controls can be used in a page
where each control is associated with a different UpdatePanel control or a single UpdateProgess
control can be associated with all UpdatePanel controls on the page. This is done by setting the
AssociatedUpdatePanelID property of the UpdateProgress control. The information to be displayed
is defined inside the ProgressTemplate tag of the UpdateProgress control. When a control inside an
UpdatePanel causes a postback to the server, any associated UpdateProgess is displayed.
Answer D is incorrect. The Timer control is an AJAX server control that is used to perform postbacks
at defined intervals. The Timer control can be used to post the complete page, or it can be used with
the UpdatePanel control to perform partial-page updates at a defined interval.