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
setProperty( (ElementPropertyDefn) prop, value );
	}
	/**
	 * Clears the local value of the property. See <code>setProperty( )</code>
	 * for details. This is equivalent to calling
	 * <code>setProperty( propName, null )</code>.
	 * <p>
	 * Part of: Property value system.
	 * 
	 * @param propName
	 *            The name of the property to set. Must be valid. Can be a
	 *            system-defined or user-defined property name.
	 */
	public void clearProperty( String propName )
	{
		setProperty( propName, null );
	}
	/**
	 * Returns the definition object for this element.
	 * <p>
	 * Part of: Meta data system.
	 * 
	 * @return The element definition. Will always be non-null in a valid build.
	 */
	public IElementDefn getDefn( )
	{
		if ( cachedDefn == null )
		{
			cachedDefn = MetaDataDictionary.getInstance( ).getElement(
					getElementName( ) );