Hi,

I am having a problem using XPath when I validate Xml documents with a schema. Basically what happens is that an XPath query doesn't return the nodes I require if a schema is used to validate the XML. I'll try and explain it as briefly as possible here. For example, look at the following XML.

<?xml version="1.0"?>
<!-- Test Comment -->
<!-- Test Comment 2 -->
<Books>
<Book>
<Title>XML Book One</Title>
<Publisher>Publisher</Publisher>
</Book>
<Book>
<Title>XML Book Two</Title>
<Publisher>Publisher</Publisher>
</Book>
</Books>

When I execute the following code 2 nodes are returned by the XPath query and this output is produced in the debug pane;

Count = 2
XML Book One
XML Book Two

XmlTextReader reader = new XmlTextReader(@"C:\books.xml");
XmlValidatingReader vreader = new XmlValidatingReader(reader);
vreader.ValidationType = ValidationType.Schema;

XPathDocument xmldoc = new System.Xml.XPath.XPathDocument(vreader);
XPathNavigator nav = xmldoc.CreateNavigator();
nav.MoveToRoot();
nav.MoveToFirstChild();

XmlNamespaceManager nsMgr = new XmlNamespaceManager(nav.NameTable);
nsMgr.AddNamespace( "ns" , nav.NamespaceURI );

XPathExpression xPathExpr = nav.Compile("//Publisher[. = 'Publisher']/parent::node()/Title");
xPathExpr.SetContext(nsMgr);
XPathNodeIterator iterator = nav.Evaluate(xPathExpr) as XPathNodeIterator;
System.Diagnostics.Debug.WriteLine("Count = " + iterator.Count.ToString());
while ( iterator.MoveNext() )
System.Diagnostics.Debug.WriteLine(iterator.Current.Value);

However, if i validate the same Xml with a schema as illustrated below;

<?xml version="1.0"?>
<!-- Test Comment -->
<!-- Test Comment 2 -->
<Books xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="uri://books Books.xsd" xmlns="uri://books">
<Book>
<Title>XML Book One</Title>
<Publisher>Publisher</Publisher>
</Book>
<Book>
<Title>XML Book Two</Title>
<Publisher>Publisher</Publisher>
</Book>
</Books>

The XML is validated by the schema without error but no nodes are returned by the XPath query. What is going wrong?

Thanks.