So my the only left complaint about XslCompiledTransform's API is the lack of Transform(IXpathNavigable, XsltArgList, XmlWriter, XmlResolver) method. That means that if by any bad chance you happen to be transforming already loaded XmlDocument or XPathDocument and need to provide XmlResolver - you can't. You will need to pass XmlReader over your XmlDocument or XPathDocument (using XPathNavigator.ReadSubTree() method) and then XslCompiledTransform will load passed XmlReader into another XPathDocument! So your source XML in memory will be duplicated with no reason.