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
* @param module
	 *            module
	 * @param prop
	 *            definition of the property to get
	 * @return The session default property value, or null if no default value
	 *         is set.
	 */
	private Object getSessionDefaultValue( Module module,
			ElementPropertyDefn prop )
	{
		if ( prop.isStyleProperty( ) )
		{
			
			return module.session.getDefaultValue( prop.getName( ) );
		}
		return null;
	}
	/**
	 * Gets selector of the given slot of this element. The selector is kind of
	 * predefined style, and its style property value can be applied on contents
	 * of the given slot of this element depending on whether property can be
	 * inherited.
	 * 
	 * @param slotID
	 *            slot id
	 * @return the selector of the given slot of this element.
	 */
	public String getSelector( int slotID )
	{
		ElementDefn defn = (ElementDefn) getDefn( );