Using XmlReader.ReadToDescendant()

Question

I'm trying to read through an XML (Actually a GML, but I don't think that makes a difference) and have been running into issues with parsing. This is my first brush with dealing in XML.

My code in C#

void ParseXML(String path)
{
    XmlReader reader = XmlReader.Create( new FileStream( path, FileMode.Open ) );

    reader.Read();

    while( reader.Read() )
    {
        // Only detect start elements.
        if ( reader.IsStartElement() && reader.Name == "gml:featureMember" )
        {
            Debug.Log(reader.Name);
            reader.ReadToDescendant("gml:featureMember");
            Debug.Log(reader["ogr:X"]);
        }
    }
}

A section from the GML I'm working with:

  <gml:featureMember>
    <ogr:fence_neighbors fid="F1">
      <ogr:Name>Xyz Xyz</ogr:Name>
      <ogr:X>2353.45361911000</ogr:X>
      <ogr:Y>-4652.36641288000</ogr:Y>
    </ogr:fence_neighbors>
  </gml:featureMember>

Making this slightly more difficult is that I am working without access to System.Xml.Linq (Unity3D). I get reader.Name just fine, but reader["ogr:X"] always comes up null. It seems like I'm not using ReadToDescendant and Reader properly, but I'm not quite sure where to start.

Answer 1

The XmlReader does not know about the namespace prefixes as you're using them.

Here is a test program that does what I think you're after. Note that the namespace URI is given explicitly.

using System;
using System.IO;
using System.Xml;


class SOTest {

    static void Main(string[] args) {
        ParseXML(args[0]);
    }

    static void ParseXML(String path)
    {
        XmlReader reader = XmlReader.Create( new FileStream( path, FileMode.Open ) );

        reader.Read();

        while( reader.Read() )
        {
            // Only detect start elements.
            if ( reader.IsStartElement() && reader.LocalName == "featureMember" && reader.NamespaceURI == "gml-namespace-uri" )
            {
                Console.WriteLine(reader.Name);
                reader.ReadToDescendant("X", "ogr-namespace-uri");
                Console.WriteLine(reader.ReadInnerXml());
            }
        }
    }
}

I added declarations to the source document for testing:

<?xml version="1.0" encoding="utf-8"?>
<wrapper xmlns:gml="gml-namespace-uri" xmlns:ogr="ogr-namespace-uri">
  <gml:featureMember>
    <ogr:fence_neighbors fid="F1">
      <ogr:Name>Xyz Xyz</ogr:Name>
      <ogr:X>2353.45361911000</ogr:X>
      <ogr:Y>-4652.36641288000</ogr:Y>
    </ogr:fence_neighbors>
  </gml:featureMember>
</wrapper>

The output is simply

gml:featureMember
2353.45361911000