StructuredDocumentTag.placeholder property. Gets the [BuildingBlock](../../../aspose.words/buildingblock/) containing placeholder text which should be displayed when this SDT run contents are empty, the associated Mapped XML element is empty as specified via the [StructuredDocumentTag.xmlMapping](../xmlMapping/) element or the [StructuredDocumentTag.isShowingPlaceholderText](../isShowingPlaceholderText/) element is ``true``....contents are empty, the associated mapped XML element is empty as specified...