XSLT: Check if any group of elements have a child element with a specified value

Consider the following XML:

<AllMyDataz>
    <Data>
       <Item1>A</Item1>
    </Data>
    <Data>
       <Item1>B</Item1>
    </Data>
    <Data>
       <Item1>A</Item1>
    </Data>
</AllMyDataz>

In my transformation I only want to do something if any 开发者_Python百科of the "Data" elements contain a child element Item1 with the value of "A". I also only want to do this one time, even if multiple "Data" elements fit the criteria.

I think I need to write a <xsl:if test=""> statement to return true if any Data/Item1 contains the value "A".

Does anyone know how to do this with an if statement or any other way?

Thank you in advance :)

-Alex

<xsl:template match="AllMyDataz">
  <xsl:if test="Data/Item1[.='A']">
    <!-- now do something -->
  </xsl:if>
</xsl:template>

The Data/Item1[.='A'] selects all the matching <Item1> nodes, resulting in a node-set.

When a node-set is used in Boolean context, it evaluates to true if it is non-empty and to false if it is empty. Exactly what you wanted.