What have I done wrong here with checking for xml nodes that don't exist?

Question

My XML:

<?xml version='1.0'?>

<bookstore xmlns="urn:newbooks-schema">

  <book genre="novel" style="hardcover">

    <title>The Handmaid's Tale</title>

    <author>

      <first-name>Margaret</first-name>

      <last-name>Atwood</last-name>

    </author>

    <price>19.95</price>

  </book>

</bookstore>

My program:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Xml;



namespace MoreXMLTesting

{

    class Program

    {

        static void Main(string[] args)

        {

            //Create the XmlDocument.

            XmlDocument doc = new XmlDocument();

            doc.Load("newbooks.xml");



            if (doc.SelectSingleNode("/bookstore/book/title") == null)

            {

                Console.WriteLine("Whelp, there aren't any new books");

            }

            if (doc.SelectSingleNode("/bookstore/coffee") == null);

            {

                Console.WriteLine("There ain't coffee at this joint");

            }



            Console.ReadKey();

        }

    }

}

I would have thought that I'd get the output of "There ain't coffee at this joint, but I also get "Whelp, there aren't any new books." What have I done wrong here with checking for xml nodes that don't exist?

EDIT:

Struggling with another aspect. What happens when there is a sub-namespace?

<?xml version='1.0'?>

<bookstore xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="C:\newbooks.xsd">

  <book genre="novel" style="hardcover">

    <title>The Handmaid's Tale</title>

    <author>

      <first-name>Margaret</first-name>

      <last-name>Atwood</last-name>

    </author>

    <price>19.95</price>

  </book>

</bookstore>

Answer 1

You need to respect and deal with the XML namespace in your XML document!

<bookstore xmlns="urn:newbooks-schema">
           ***************************

Try this code:

// Create the XmlDocument.
XmlDocument doc = new XmlDocument();

// Create the XML Namespace Manager and initialize it    
XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("ns", "urn:newbooks-schema");

doc.Load("newbooks.xml");

// *USE* the namespace prefix as defined by your "nsmgr" in your XPath
if (doc.SelectSingleNode("/ns:bookstore/ns:book/ns:title", nsmgr) == null)
{
    Console.WriteLine("Whelp, there aren't any new books");
}

if (doc.SelectSingleNode("/ns:bookstore/ns:coffee", nsmgr) == null) ;
{
    Console.WriteLine("There ain't coffee at this joint");
}

What have I done wrong here with checking for xml nodes that don't exist?

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