XPathReader is/ was an implementation of a forward reading XML parser (built on XMLReader) which allowed you to register XPath queries for it to find (or at least a subset of XPath called Sequential XPath). This seems to be the perfect choice for easy access to elements of xml streams, or case where you just need to pull some information out of the start of a large xml document and therefore don't want to load the whole thing into memory.
There seemed to be a flurry of excitement about the open source implementation that one of the MS guys was releasing back in 2003/ 2004, eg:
http://donxml.com/allthingstechie/archive/2004/02/26/430.aspx
http://msdn.microsoft.com/en-us/library/ms950778.aspx
http://www.tkachenko.com/blog/archives/000472.html
But after that the trail seems to dry up. The references to where the implementation was hosted (http://workspaces.gotdotnet.com/xpathreader) no longer seem to work. Does anyone know what happened to it, and why the interested disappeared?
XNode.ReadFrom combines the power (and supported status) of Linq to XML with the ability to process a stream rather than loading the entire file into memory
http://msdn.microsoft.com/en-us/library/system.xml.linq.xnode.readfrom.aspx
It seems that ms released this over here and the install includes source code.
I suspect that LINQ-to-XML happened. However, the Mvp.Xml project on CodePlex has many features that relate to this. You might want to take a look at the XPointer.NET library they have developed and the XPointerReader.
Also, you might want to take a look at this FastXPathReader on CodeProject (I don't know how effective it is).
As for XPathReader, all I could find were the links you provided and links associated with those. It looks like it disappeared. Like I said, I think LINQ-to-XML was the outcome, but I'm just guessing.
Found myself asking the very same question today as I was meaning to build a BizTalk pipeline component to parse incoming message for specific elements.
After some googling, I found out that the XPathReader assembly is shipped with BizTalk and is residing in the GAC.
Just reference the GAC assembly Microsoft.BizTalk.XPathReader.dll and you're up and running!
来源：https://stackoverflow.com/questions/465237/what-ever-happened-to-xpathreader