Sys.WebForms.PageLoadingEventArgs panelsUpdating Property
Gets an array of HTML <div> elements that represent UpdatePanel controls that will be updated in the DOM as a result of the current asynchronous postback.
To get or set property values for client API properties, you must call property accessor methods that are named with the get_ and set_ prefixes. For example, to get or set a value for a property such as cancel, you call the get_cancel or set_cancel methods.
var arr = eventArgs.get_panelsUpdating()
An array of <div> elements that will be updated in the DOM. If no elements will be updated, the property returns null.
If the contents of any UpdatePanel controls will be updated as the result of a partial-page update, the panelsUpdating property contains an array that references the corresponding <div> elements. The pageLoading event of the Sys.WebForms.PageRequestManager class uses a PageLoadingEventArgs object to return its event data.