Querying a sitemap with LINQ to XML

Question

I have an ASP.NET MVC website. This website has a sitemap that looks like the following:

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>http://www.mysite.com/contact</loc>
    <lastmod>2013-06-04</lastmod>
    <changefreq>never</changefreq>
  </url>
  <url>
    <loc>http://www.mysite.com/contact-us</loc>
    <lastmod>2013-06-04</lastmod>
    <changefreq>never</changefreq>
  </url>
  <url>
    <loc>http://www.mysite.com/about/books</loc>
    <lastmod>2013-06-18</lastmod>
    <changefreq>monthly</changefreq>
  </url>
  <url>
    <loc>http://www.mysite.com/about/blog</loc>
    <lastmod>2012-05-02</lastmod>
    <changefreq>never</changefreq>
  </url>
  <url>
    <loc>http://www.mysite.com/about/blog/post-1</loc>
    <lastmod>2012-05-02</lastmod>
    <changefreq>never</changefreq>
  </url>
  <url>
    <loc>http://www.mysite.com/about/blog/post-2</loc>
    <lastmod>2012-02-15</lastmod>
    <changefreq>never</changefreq>
  </url>
</urlset>

I'm trying to figure out how to query this sitemap with Linq-to-XML in C#. I'm trying to write a query that returns only the blog post entries. The blog post entries are the ones whose loc attribute value starts with http://www.mysite.com/about/blog/. Currently, I'm successfully loading and querying the sitemap. However, I can't figure out how to filter down to just the blog posts and then sort by the lastmod value. This is what I have so far:

XDocument sitemap = XDocument.Load(Server.MapPath("/resources/sitemap.xml"));
IEnumerable<XElement> blogs = from post in sitemap.Descendants("url")
                              select post;

How do I filter down to just my blog posts? My query for even just the urls doesn't seem to be working.

Answer 1

Your XML document uses default namespace, so you have to use it in your query too:

var ns = XNamespace.Get("http://www.sitemaps.org/schemas/sitemap/0.9");

IEnumerable<XElement> blogs = from post in sitemap.Root.Elements(ns + "url")
                              where ((string)post.Element(ns + "loc") ?? string.Empty).StartsWith("http://www.mysite.com/about/blog/")
                              select post;

I used ((string)post.Element(ns + "loc") ?? string.Empty) to make sure no exception is being thrown when <loc> element does not exist, but if you're sure that every <url> has <loc> in it you can replace that with just ((string)post.Element(ns + "loc")).