Question

Relating to this question, is it possible to use variables inside xsl:key? I want to do smth like this:

<xsl:key name="ChargesKey" match="$ChargesForDisplay/charge" use="Name"/>

I’m using XSLT 1.0 with ASP.Net

Answer 1

I believe I can safely assume that you are referring to dynamically-generated node-set variables (as opposed to those selected from the source DOM, which are trivial), and yes it is possible to perform a key-match on the contents of a dynamically generated node-set variable (as I demonstrate for this question).

Assuming you have a variable like this:

<xsl:variable name="ChargesForDisplay">
<charge>
   <Name>Name1</Name>
</charge>
<charge>
   <Name>Name2</Name>
</charge>
<charge>
   <Name>Name1</Name>
</charge>
<charge>
   <Name>Name3</Name>
</charge>
</xsl:variable>

You would define the key like this:

<xsl:key name="ChargesKey" match="charge" use="Name"/>

And then you can apply it like this:

  <xsl:template match="/">
      <xsl:apply-templates select="msxsl:node-set($ChargesForDisplay)" />
  </xsl:template>

  <xsl:template
   match="charge[generate-id(.)=generate-id(key('ChargesKey',Name)[1])]">
    <xsl:variable name="matchingItems" select="key('ChargesKey', Name)" />
    ...
  </xsl:template>

Of course, if the variable contains a selection of nodes from the source XML DOM, then it’s just the same approach, except you don’t need to use msxsl:node-set().

I suspect that having a key on a node-name that’s also present in the source XML document or multiple dynamically-generated node-set variables may cause grouping to produce unexpected results(because the key() function would locate nodes from both the variable and the source document). For this reason, I’d suggest defining keys on nodes that would only be present in one particular variable and nowhere else.