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
SlotDefn slotDefn = (SlotDefn) defn.getSlot( slotID );
		if ( slotDefn == null )
		{
			return null;
		}
		String slotSelector = slotDefn.getSelector( );
		if ( StringUtil.isBlank( slotSelector ) )
		{
			return null;
		}
		return slotSelector;
	}
	/**
	 * Returns property value with predefined style.
	 * 
	 * @param module
	 *            module
	 * @param prop
	 *            definition of property to get
	 * @param selector
	 *            predefined style
	 * @return The property value, or null if no value is set.
	 */
	public Object getPropertyFromSelector( Module module,
			ElementPropertyDefn prop, String selector )
	{
		assert module != null;
		if ( selector == null )
			return null;