distinct in Xpath?

I have this XML file, from which I'd like to count the number of users referenced in it. But they can appear in more than one category, and I'd like these duplicates not to be taken into account.

In the example below, the query should return 3 and not 4. Is there a way in XPath to do so? Users are not sorted at all.

<list>
  <开发者_如何学Gogroup name='QA'>
    <user name='name1'>name1@email</user>
    <user name='name2'>name2@email</user>
  </group>
  <group name='DEV'>
    <user name='name3'>name3@email</user>
    <user name='name2'>name2@email</user>
  </group>
</list>

A pure XPath 1.0 -- one-liner:

Use:

count(/*/group/user[not(. = ../following-sibling::group/user)])

using the functions namespace http://www.w3.org/2005/xpath-functions you can use

distinct-values(//list/group/user)

UPDATE:

At the top of your xsl/xslt file you should have a stylesheet element, map the url above to the prefix fn as below...

<xsl:stylesheet version="1.0"
 xmlns:fn="http://www.w3.org/2005/xpath-functions"
 >

then you can use

select="fn:distinct-values(//list/group/user)"

this would assume you are doing this in templates and not in some xpathdocument object inwhich case you need to use a namespacemanager class.

links...

XSLT: Add namespace to root element

http://www.xqueryfunctions.com/xq/fn_distinct-values.html

http://msdn.microsoft.com/en-us/library/d6730bwt(VS.80).aspx

Otherwise try Dimitre Novatchev's answer.

I have a better answer

count(//user[not(. = following::user/.)])

Not sure if you could do it in XPath, but it could be done easily using System.Linq:

string xml = "<list><group name='QA'><user name='name1'>name1@email</user><user name='name2'>name2@email</user></group><group name='DEV'><user name='name3'>name3@email</user><user name='name2'>name2@email</user></group></list>";
        XElement xe = XElement.Parse(xml);
        int distinctCount = xe.Elements().Elements().Select(n => n.Value).Distinct().Count();

In this example, distinctCount will equal 3.

You will need to use two functions like this.

count(distinct-values(//list/group/user))

First get the distinct values, then count them

count(//user[not(./@name = preceding::user/@name)])

I think the best way is to try to draw your xml data on paper to see how you can solve it easily