从具有多个名称空间的XML反序列化选择元素

Question

I am trying to deserialize an XML document that has mostly extraneous information. The classes I have created reflect the what information I am trying to pick out of the document.

When I actually do the deserialization, the deserialiation appears to be successful but the CraigslistChannel and CraigslistItem variables always end up being null, even though the document clear has those elements in them.

The XML document that I am trying to deserialize can be found here: https://limaohio.craigslist.org/search/ctd?format=rss&s=25

And looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 xmlns="http://purl.org/rss/1.0/"
 xmlns:enc="http://purl.oclc.org/net/rss_2.0/enc#"
 xmlns:ev="http://purl.org/rss/1.0/modules/event/"
 xmlns:content="http://purl.org/rss/1.0/modules/content/"
 xmlns:dcterms="http://purl.org/dc/terms/"
 xmlns:syn="http://purl.org/rss/1.0/modules/syndication/"
 xmlns:dc="http://purl.org/dc/elements/1.1/"
 xmlns:taxo="http://purl.org/rss/1.0/modules/taxonomy/"
 xmlns:admin="http://webns.net/mvcb/"
>

<channel rdf:about="https://sfbay.craigslist.org/search/sfc/ctd?format=rss">
<title>craigslist SF bay area | cars &#x26; trucks - by dealer search </title>
<link>https://sfbay.craigslist.org/search/sfc/ctd</link>
<description></description>
<dc:language>en-us</dc:language>
<dc:rights>copyright 2016 craiglist</dc:rights>
<dc:publisher>robot@craigslist.org</dc:publisher>
<dc:creator>robot@craigslist.org</dc:creator>
<dc:source>https://sfbay.craigslist.org/search/sfc/ctd?format=rss</dc:source>
<dc:title>craigslist SF bay area | cars &#x26; trucks - by dealer search </dc:title>
<dc:type>Collection</dc:type>
<syn:updateBase>2016-08-29T07:55:51-07:00</syn:updateBase>
<syn:updateFrequency>1</syn:updateFrequency>
<syn:updatePeriod>hourly</syn:updatePeriod>
<items>
 <rdf:Seq>
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755852598.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755847263.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755845763.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755841763.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755839975.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755836851.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755833170.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755831622.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755807313.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755759606.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755718561.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755713440.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755710804.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755708355.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755706051.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755706053.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755689225.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755671023.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755669710.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755668546.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755667302.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755666084.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755664804.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755663619.html" />
  <rdf:li rdf:resource="http://sfbay.craigslist.org/sfc/ctd/5755662504.html" />
 </rdf:Seq>
</items>
</channel>
<item rdf:about="http://sfbay.craigslist.org/sfc/ctd/5755852598.html">
<title><![CDATA[2013 *Ford* *Mustang* *2dr Coupe* -$26,899 (Certified Pre-Owned, Financing Available) &#x0024;26899]]></title>
<link>http://sfbay.craigslist.org/sfc/ctd/5755852598.html</link>
<description><![CDATA[*2013* *Ford* *Mustang* *2dr Coupe* - $26,899* (2013* *Ford* *Mustang* *2dr Coupe*) 
Phone: 
 <a href="/fb/sfo/ctd/5755852598" class="showcontact" title="click to show contact info">show contact info</a>

Price: $26,899 
Vehicle Information Overview 
Year: 2013 
Make: Ford 
Model: Mustang 
Trim: 2dr Coupe 
VIN: 1ZVBP8CF0D5271908 
Mileage: 15500 
B [...]]]></description>
<dc:date>2016-08-29T06:53:28-07:00</dc:date>
<dc:language>en-us</dc:language>
<dc:rights>copyright 2016 craiglist</dc:rights>
<dc:source>http://sfbay.craigslist.org/sfc/ctd/5755852598.html</dc:source>
<dc:title><![CDATA[2013 *Ford* *Mustang* *2dr Coupe* -$26,899 (Certified Pre-Owned, Financing Available) &#x0024;26899]]></dc:title>
<dc:type>text</dc:type>
<enc:enclosure resource="https://images.craigslist.org/00404_h6HxiFEMymk_300x300.jpg" type="image/jpeg"/>
<dcterms:issued>2016-08-29T06:53:28-07:00</dcterms:issued>
</item>
</rdf:RDF>

Here is my code:

String requestURL = "https://limaohio.craigslist.org/search/ctd?format=rss&s=25";
IHttpWebResponse response = (new HttpRequesterWrapper(4000)).GetWebResponse(requestURL);
if (!String.IsNullOrEmpty(response.HTML))
{
    XmlSerializer serializer = new XmlSerializer(typeof(CraigslistRDF));
    using (TextReader sr = new StringReader(response.HTML))
    {
        CraigslistRDF rss = (CraigslistRDF)serializer.Deserialize(sr);
        if (rss != null && rss.Channel != null)
        {
            var a = 1;
        }
    }
}

And most importantly, here are the classes that I am trying to deserialize with:

[XmlRoot(ElementName = "RDF", Namespace = "http://www.w3.org/1999/02/22-rdf-syntax-ns#")]
public class CraigslistRDF
{
    [XmlElement("channel")]
    public CraigslistChannel Channel;

    [XmlElement("item")]
    public CraigslistItem[] Items;
}

[XmlRoot("channel")]
public class CraigslistChannel
{
    [XmlAttribute(AttributeName = "about", Namespace = "http://www.w3.org/1999/02/22-rdf-syntax-ns#")]
    public String About;

    [XmlElement("title")]
    public String Title;

    [XmlElement("link")]
    public String Link;

    [XmlElement("description")]
    public String Description;
}

[XmlRoot("item")]
public class CraigslistItem
{
    [XmlAttribute(AttributeName = "about", Namespace = "http://www.w3.org/1999/02/22-rdf-syntax-ns#")]
    public String About;

    [XmlElement("title")]
    public String Title;

    [XmlElement("link")]
    public String Link;

    [XmlElement("description")]
    public String Description;

    [XmlElement(ElementName = "source", Namespace = "http://purl.org/dc/elements/1.1/")]
    public String Source;
}

Does anyone have any insight into why the CraigslistChannel and CraigslistItem properties always end up being null?

Any help would be greatly appreciated.

Answer 1

Because your channel and item elements do have a namespace. The default namespace is declared in the root element as http://purl.org/rss/1.0/ , so change your attributes to match this:

[XmlRoot(ElementName = "RDF", Namespace = "http://www.w3.org/1999/02/22-rdf-syntax-ns#")]
public class CraigslistRDF
{
    [XmlElement("channel", Namespace = "http://purl.org/rss/1.0/")]
    public CraigslistChannel Channel;

    [XmlElement("item", Namespace = "http://purl.org/rss/1.0/")]
    public CraigslistItem[] Items;
}

As an aside, the [XmlRoot("item")] and [XmlRoot("channel")] attributes aren't used and can be removed (these classes aren't used as the root).

Answer 2

Try xml linq

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        const string FILEMNAME = @"c:\temp\test.xml";
        static void Main(string[] args)
        {
            XDocument doc = XDocument.Load(FILEMNAME);
            XElement rdf = (XElement)doc.FirstNode;
            XNamespace rdfNs = rdf.GetNamespaceOfPrefix("rdf");
            XNamespace dcNs = rdf.GetNamespaceOfPrefix("dc");
            XNamespace defaultNs = rdf.GetDefaultNamespace();

            CraigslistRDF craigslistRDF = rdf.Elements(defaultNs + "channel").Select(x => new CraigslistRDF
            {
                Channel = new CraigslistChannel() {
                    About = (string)x.Attribute(rdfNs + "about"),
                    Description = (string)x.Elements(defaultNs + "description").FirstOrDefault(),
                    Link =  (string)x.Element(defaultNs + "link"),
                    Title =  (string)x.Element(defaultNs + "title")
                },

            }).FirstOrDefault();

            craigslistRDF.Items = rdf.Elements(defaultNs + "item").Select(x => new CraigslistItem()
            {
                About = (string)x.Attribute(rdfNs + "about"),
                Description = (string)x.Elements(defaultNs + "description").FirstOrDefault(),
                Link = (string)x.Element(defaultNs + "link"),
                Source = (string)x.Element(dcNs + "source"),
                Title = (string)x.Element(defaultNs + "title")
            }).ToArray();

        }
    }

    public class CraigslistRDF
    {
        public CraigslistChannel Channel { get; set; }
        public CraigslistItem[] Items { get; set; }
    }

    public class CraigslistChannel
    {
        public String About { get; set; }
        public String Title { get; set; }
        public String Link { get; set; }
        public String Description { get; set; }
    }

    public class CraigslistItem
    {
        public String About { get; set; }
        public String Title { get; set; }
        public String Link { get; set; }
        public String Description { get; set; }
        public String Source { get; set; }
    }
}