Bug 121352 The data set binding property cannot be retrieved in report preview layout
In report preview page, the datasource/dataset property binding lists cannot be retrieved. The dataset binding can not work correctly in layout preview because it's value cannot get from the binding list. But in the data set edit page, the binding value can be got. You can refer to the attachment.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
*/
	public void clearListeners( )
	{
		if ( listeners != null )
			listeners.clear( );
		listeners = null;
	}
	/**
	 * Sends an event called by the notification framework. The default
	 * implementation sends the event to listeners of this one object. Derived
	 * classes override this to send it to additional associated objects
	 * depending on context. The subclass should set the event's delivery path
	 * to indicate these additional delivery routes.
	 * <p>
	 * Part of: Notification system.
	 * 
	 * @param ev
	 *            the event to send
	 */
	public void sendEvent( NotificationEvent ev )
	{
		ev.setDeliveryPath( NotificationEvent.DIRECT );
		broadcast( ev );
	}
	/**
	 * Gets the root node of the design tree. This node must be a instance of
	 * <code>ReportDesign</code> or <code>Library</code>.
	 * 
	 * @return the root node of the design tree
	 */