The ReadInnerXML and ReadOuterXml methods of the System.Xml.XmlReader class now validate the content they return against a schema or DTD if present.
Several overloads of the the Load and Transform methods of the System.Xml.Xsl.XslTransform class are now obsolete. Stylesheets should be loaded through an instance of the existing XmlUrlResolver class or the new XmlSecureResolver class unless they are from a fully trusted source.
New overloads are available for the System.Xml.Schema.XmlSchema.Compile method and the System.Xml.Schema.XmlSchemaCollection.Add method that accept an XmlUrlResolver or XmlSecureResolver instance.