Write handler for the AsyncPostBackError event on ScriptManager control.
Can use AsyncPostBackErrorMessage property of ScriptManager to display error message to user when partial-page update error occurs.
Provides info to user during partial-page update, e.g. animated GIF to indicate system is processing.
Place within the ContentTemplate element of UpdatePanel.
Content within ProgressTemplate element could be image, text, or other HTML content that will be shown whilst partial-page updated is executing.
Can also associate with UpdatePanel via the AssociatedUpdatePanelId property - thus use single UpdateProgress Control to handle multiple UpdatePanels.
By default appears .5 second after partial page update starts. Can use DisplayAfter property to specify a different number of milliseconds to delay appearance.
Can abort async postback processing by adding Cancel button to the UpdateProgress control and from its event handler calling the abortPostBack method of the PageRequestManager class.
Update portions of page on periodic basis, e.g. for advertisement, stock ticker, etc.
Can add to ContentTemplate of UpdatePanel, timer will then trigger partial-page update of UpdatePanel. Once postback processing complete the timer is reset.
Can also be defined outside of UpdatePanel and user Trigger control within UpdatePanel to form the association. Outside of an UpdatePanel the timer is reset the moment it is raised. If another timed interval elapses whilst postback is still being processed then first postback is cancelled.