IStructuredDocumentTag.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 [IStructuredDocumentTag.xmlMapping](../xmlMapping/) element or the [IStructuredDocumentTag.isShowingPlaceholderText](../isShowingPlaceholderText/) element is true....Markup class IStructuredDocumentT...