Even though xlsgen cannot directly import an XML file, it's easy to transform an XML file into a CSV file thanks to a XSL stylesheet, and then import the CSV file itself. Here is an example of how it works. Let's say we have :

• An input XML file called books.xml, which as the name suggests is a collection of book titles
  
• An XSL stylesheet called books_csv.xsl, which transforms the XML file into a CSV file
• We are not interested in all fields of books.xml, rather we are interested in the ISBN, the title and the author's last name
• The CSV file will use the comma (,) as a field separator. We need to make sure during the XML-to-CSV transform that whenever data includes a comma, it has to be enclosed in double-quotes so that it meets the rules of a regular CSV file (disambiguates the separator and actual content).

Here is books.xml :

<?xml version='1.0'?>
<!-- This file represents a fragment of a book store inventory database -->
<bookstore>
  <book genre="autobiography" publicationdate="1981" ISBN="1-861003-11-0">
    <title>The Autobiography, of Benjamin Franklin</title>
    <author>
      <first-name>Benjamin</first-name>
      <last-name>Franklin</last-name>
    </author>
    <price>8.99</price>
  </book>
  <book genre="novel" publicationdate="1967" ISBN="0-201-63361-2">
    <title>The Confidence Man</title>
    <author>
      <first-name>Herman</first-name>
      <last-name>Melville</last-name>
    </author>
    <price>11.99</price>
  </book>
  <book genre="philosophy" publicationdate="1991" ISBN="1-861001-57-6">
    <title>The Gorgias</title>
    <author>
      <name>Plato</name>
    </author>
    <price>9.99</price>
  </book>
</bookstore>

Here is the XSL stylesheet books_csv.xsl :

<!DOCTYPE stylesheet [
<!ENTITY newln "&#xD;&#xA;">
]>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:output method="text" encoding="utf-8"/>

    <xsl:template match="bookstore">
       <xsl:apply-templates select="book"/>
    </xsl:template>

    <xsl:template match="book">
       <xsl:if test="contains(@ISBN, ',')">&quot;</xsl:if>
       <xsl:value-of select="@ISBN"/>
       <xsl:if test="contains(@ISBN, ',')">&quot;</xsl:if>
       <xsl:text>,</xsl:text>
       <xsl:if test="contains(title, ',')">&quot;</xsl:if>
       <xsl:value-of select="title"/>
       <xsl:if test="contains(title, ',')">&quot;</xsl:if>
       <xsl:text>,</xsl:text>
       <xsl:apply-templates select="author"/>
       <xsl:text>&newln;</xsl:text>
    </xsl:template>

    <xsl:template match="author">
       <xsl:apply-templates select="last-name"/>
       <xsl:apply-templates select="name"/>
    </xsl:template>

    <xsl:template match="last-name">
       <xsl:if test="contains(., ',')">&quot;</xsl:if>
       <xsl:value-of select="."/>
       <xsl:if test="contains(., ',')">&quot;</xsl:if>
    </xsl:template>

    <xsl:template match="name">
       <xsl:if test="contains(., ',')">&quot;</xsl:if>
       <xsl:value-of select="."/>
       <xsl:if test="contains(., ',')">&quot;</xsl:if>
    </xsl:template>

</xsl:stylesheet>

Note :

• This stylesheet is obviously designed to process books.xml. If the XML file used a different schema, a specifically designed stylesheet would be needed. There is no general purpose stylesheet to be used unfortunately, which means anyone willing to transform XML into CSV will have to get decent knowledge on Xpath expressions and XSLT transforms.
• This stylesheet has many xls:if statements in it that are meant to try to catch whether the content uses commas, the field separator, in which case the content must be enclosed in double-quotes.
• The stylesheet takes into account the fact that not every author's name has a last name, sometimes it's just a name.
• We insert a newline after all fields of the current record are done.

XSLT processors are common on every single programming platform. In the following, we are going to use the XSLT processor that is part of the .NET run-time, but suffice to say there are many others (for instance, for C/C++ developers, there is libxslt).

The following .NET code simply processes the transform :

using System.IO;
using System.Xml;
using System.Xml.Xsl;
using System.Xml.XPath;

XPathDocument input = new XPathDocument ("books.xml"); // input XML file

XslTransform trans = new XslTransform();
trans.Load("books_csv.xsl"); // XSL stylesheet

XmlTextWriter destination = new XmlTextWriter("result.csv", null); // output CSV file
trans.Transform(input, null, destination);
destination.Close();

And the resulting CSV file is :

1-861003-11-0,"The Autobiography, of Benjamin Franklin",Franklin
0-201-63361-2,The Confidence Man,Melville
1-861001-57-6,The Gorgias,Plato

With the CSV file in hands, it's now possible to import it in xlsgen directly. How it works is explained here.