XML / XSL

<section>
  <A>Text A</A>
  <A>Text A 2</A>
  <B>Text C</B>
  <C>Text C</C>
  <D>Text D</D>
</section>

<xsl:stylesheet version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
      extension-element-prefixes="redirect">

<xsl:template match="section">
   <xsl:element name="test">
      <xsl:element name="processed">
        <xsl:apply-templates mode="normal"/>
      </xsl:element>
      <xsl:element name="not-processed">
        <xsl:apply-templates mode="show-not-processed"/>
      </xsl:element>
    </xsl:element>
</xsl:template>

<xsl:template match="A" mode="normal">
   <xsl:value-of select="name()"/>
</xsl:template>
<xsl:template match="C" mode="normal">
   <xsl:value-of select="name()"/>
</xsl:template>
<xsl:template match="A|C" mode="show-not-processed"/>


<xsl:template match="*" mode="normal"/>


<xsl:template match="*" mode="show-not-processed">
   <xsl:value-of select="name()"/>
</xsl:template>


</xsl:stylesheet >

<?xml version="1.0" encoding="UTF-8"?>
<test><processed>
  A
  A
  
  C
  
</processed><not-processed>
  
  
  B
  
  D
</not-processed></test>

<xsl:template match="A|C" mode="show-not-processed"/>

---

"When the only tool you have is a hammer, a sore thumb you will have."

public XmlNodeList Search(string input)
{
  string query = "/mainnode/subnode/[name = " + input.Trim().ToString() + "]";
  XmlDocument doc = new XmlDocument();
  doc.Load("mydata.xml");
  XmlNodeList nodes = doc.SelectNodes(query);
  return nodes;
}

"/store/books[position() <= 5]"