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
{
		return isValid;
	}
	/**
	 * Sets whether the element is valid.
	 * 
	 * @param isValid
	 *            the valid to set
	 */
	public void setValid( boolean isValid )
	{
		this.isValid = isValid;
	}
	/**
	 * Returns the display label of this element. To get the display label of an
	 * element, the following step should be done:
	 * <ul>
	 * <li>The localized display name of this element if set</li>
	 * <li>The display property value of this element if set</li>
	 * <li>The name of element if set</li>
	 * <li>The localized display name of this kind of element, which is defined
	 * in metadata, if set</li>
	 * <li>The name of this kind of element, which is also defined in metadata
	 * </li>
	 * </ul>
	 * <p>
	 * User can also decide at which detail level the display label should be
	 * returned. The level could be one of the following 3 options:
	 * <ul>
	 * <li>USER_LABEL: Only the first 3 steps can be visited, if not found,