Computing a value from an XPathNavigator

Question

I am trying to write a function for my XSL Transform.

Basically within the function I have a System.Xml.XPath.XPathNodeIterator and I want to get the value of an XPath when applied to each of the nodes within that iterator.

In this instance the XPath is concat(name(.) , "_", string(.)) but it could actually be anything.

This is throwing an XPathException: "Expression must evaluate to a node-set." Which kind of makes some sense

I suspect I'm going to be told this is not a valid XPath but is some other xml/xsl related functionality however, consider that in XSL I can do this:

<xsl:value-of select="concat(name(.) , "_", string(.))"/>

And that is what I'm after - but within the function.

I'm using C# but VB answers are acceptable.

System.Xml.XPath.XPathNodeIterator Nodes = whatever;
string KeySelector="concat(name(.), '_', string(.))";
while (Nodes.MoveNext())
{
    System.Xml.XPath.XPathNavigator xpnValue = Nodes.Current.SelectSingleNode(KeySelector);
}

Answer 1

You will need to use the Evaluate method and not SelectSingleNode. And the result of your XPath is not an XPathNavigator, it is an XPath String respectively a .NET System.String or a C# string.