Sys.CancelEventArgs cancel Property
Gets or sets a value that specifies whether the event source should cancel the operation that caused the event.
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 isCanceled = eventArgs.get_cancel();
true to request that the event be canceled; otherwise, false. The default is false.