c# - Computing a value from an XPathNavigator -

i trying write function xsl transform.

basically within function have system.xml.xpath.xpathnodeiterator , want value of xpath when applied each of nodes within iterator.

in instance xpath concat(name(.) , "_", string(.)) anything.

this throwing xpathexception: "expression must evaluate node-set." kind of makes sense

i suspect i'm going told not valid xpath other xml/xsl related functionality however, consider in xsl can this:

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

and i'm after - within function.

i'm using c# vb answers acceptable.

system.xml.xpath.xpathnodeiterator nodes = whatever; string keyselector="concat(name(.), '_', string(.))"; while (nodes.movenext()) {     system.xml.xpath.xpathnavigator xpnvalue = nodes.current.selectsinglenode(keyselector); } 

you need use evaluate method , not selectsinglenode. , result of xpath not xpathnavigator, xpath string respectively .net system.string or c# string.