Attribute cannot be added after a sub-element node

Background

The other day, I was working on an XSLT that transforms XML into HTML page. By fluke or some other means I got this error I wasn’t prepared for:

Error

Attribute and namespace nodes cannot be added to the parent element after a text, comment, pi, or sub-element node has already been added.

XSLT Source Code

I repeated the error by creating this XSLT code.

<xsl:template match=/Books>

<html>
<body>
<h2>Select a book to read today:</h2>
<xsl:element name=select>

<xsl:attribute name=name>books</xsl:attribute>

<xsl:for-each select=Book>

<xsl:element name=option>

<xsl:value-of select=Title/>

<xsl:attribute name=value>

<xsl:value-of select=Title/>

</xsl:attribute>

</xsl:element>

</xsl:for-each>

<xsl:element name=select>

</xsl:element>

</xsl:element>

</body>

</html>

</xsl:template>

XML Input

<Books>

<Book>
<Title>OOP Demystified</Title>
<Author>James Keogh</Author>
<Language>English</Language></Book>

<Book>
<Title>Spoken from the Heart</Title>
<Author>Laura Bush</Author><Language>English</Language>

</Book>

</Books>

Solution

The error message is self-explanatory really. To get round this problem, we need to move “<xsl:value-of select=Title/>”

to after the attributes we wish to set. This is because the attributes for that element will need to be set first before all the

values are set.

<xsl:template match=/Books>

<html>

<body>

<h2>Select a book to read today:</h2>

<xsl:element name=select>

<xsl:attribute name=name>books</xsl:attribute>

<xsl:for-each select=Book>

<xsl:element name=option>

<xsl:attribute name=value>

<xsl:value-of select=Title/>

</xsl:attribute>

<xsl:value-of select=Title/> <!– Move to here, after attribute –>

</xsl:element>

</xsl:for-each>

<xsl:element name=select“/>

</xsl:element>

</body>

</html>

</xsl:template>

Tips

  1. Debug your XSLT by opening it in Visual Studio.
  2. Point to the input XML from the Properties window for the XSLT page.
  3. Put breakpoint as you would normally do.
  4. Transform the XML by clicking Debug XSLT in the XML Editor on the toolbar. Don’t press F5/F6!
  5. Then you could start to use your usual debugging keys like F10, F11, etc.

Have fun debugging your XSLT!

One thought on “Attribute cannot be added after a sub-element node”

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