via Oleg Tkachenko @ http://www.tkachenko.com/blog/archives/000711.html
Saxon, famous XSLT 2.0 and XQuery processor, supports XInclude since version 8.9. But in Java version only! When I first heard about it I thought "I have good XInclude implementation for .NET in Mvp.Xml library, let's check out if Saxon on .NET works with XInclude.NET". I did some testing only to find out that they didn't play well together.
Turned out Saxon (or JAXP port to .NET, don't remember) relies on somewhat rarely used in .NET XmlReader.GetAttribute(int) method (yes, accessing attribute by index), and XIncludingReader had a bug in this method.
Finally I fixed it and so XIncludingReader from recently released Mvp.Xml library v2.3 works fine with Saxon on .NET.--