Trying to select all cd elements whose releasedate is on a specific month using
doc.Selectnodes("/cd/releasedate[fn:month-from-date(.)=04]")
but I always get this exception

Unhandled Exception: System.Xml.XPath.XPathException: XsltContext is needed for
this query because of an unknown function.

How do I fix this? I am using this sample xml:

<catalog>
<cd>
    <title>Empire Burlesque</title>
    <artist>Bob Dylan</artist>
    <country>USA</country>
    <company>Columbia</company>
    <price>10.90</price>
    <year>1985</year>
    <releasedate>2008-04-06T11:03:02</releasedate>
  </cd>
  <cd format="vcd">
    <title>VCD Empire Burlesque</title>
    <artist>VCD Bob Dylan</artist>
    <country>USA</country>
    <company>Columbia</company>
    <price>10.90</price>
    <year>1985</year>
    <releasedate>2008-05-08T11:03:02</releasedate>
  </cd>
</catalog>

__________________
\"Dont you ever give up!\"

fn:month-from-date is a function, in a namespace defined by the prefix "fn". But you don't define the "fn" prefix. You probably need to pass in a XmlNamespaceManager instance as a second parameter to the SelectNodes method.

/- Sam Judson : Wrox Technical Editor -/

XmlDocument doc = new XmlDocument();
            doc.Load(@"..\..\x1.xml");
            XmlNamespaceManager man = new XmlNamespaceManager(doc.NameTable);
            xmlns:fn="http://www.w3.org/2005/02/xpath-functions"
            xmlns:xs="http://www.w3.org/2001/XMLSchema"
            man.AddNamespace("fn", "http://www.w3.org/2005/02/xpath-functions");
            man.AddNamespace("xs", "http://www.w3.org/2001/XMLSchema");
            man.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");

            XmlNodeList nodes = doc.DocumentElement.SelectNodes(xpath,man);

Yes, I have tried this too, but without any lock..


"Dont you ever give up!"

You are linking to the XPATH 2.0 functions - .Net Framework only support XPATH 1.0.

/- Sam Judson : Wrox Technical Editor -/

The name of the exception System.Xml.XPath.XPathException suggests that you are trying to do this using the XPath engine in .NET (it seems to be an endemic problem on this forum that people expect us to guess what products they are using...). This engine only supports XPath 1.0, which has no month-from-date() function.

Try Saxon instead, which runs under .NET and supports XPath 2.0.

Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference