In declarative scenarios, the XmlDataSource.Transform property is specified as a multiline inner property of the System.Web.UI.WebControls.XmlDataSource object. An inner property is compatible with XSL style sheet data, because it enables you to format the style sheet in any way and ignore character padding issues such as padding quote characters.

If both the XmlDataSource.TransformFile and XmlDataSource.Transform properties are set, the XmlDataSource.TransformFile property takes precedence and the data in the XSL style sheet file (.xsl) is used instead of the style sheet elements specified in the XmlDataSource.Transform property. If an XPath expression is set using the XmlDataSource.XPath property, it is applied after the XML data is transformed.

If you change the value of the XmlDataSource.Transform property, the System.Web.UI.IDataSource.DataSourceChanged event is raised. If caching is enabled and you change the value of XmlDataSource.Transform, the cache is invalidated.