SitemapController

public class SitemapController : RenderMvcController
{
    public ActionResult SitemapXml()
    {
        var startNode = CurrentPage.Site();
        if (startNode != null)
        {
            var sitemapService = new UmbracoSitemapService();
            var items = sitemapService.GetItemsAsList(startNode.Id);

            XNamespace xn = "http://www.sitemaps.org/schemas/sitemap/0.9";
            var doc = new XDocument(new XDeclaration("1.0", "utf-8", "yes"));
            var urlSet = new XElement(xn + "urlset");
            urlSet.Add(new XAttribute("xmlns", "http://www.sitemaps.org/schemas/sitemap/0.9"));
            foreach (var item in items)
            {
                urlSet.Add(new XElement(xn + "url", new XElement(xn + "loc", item.Url),
                    new XElement(xn + "lastmod", item.LastUpdateDate)));
            }

            doc.Add(urlSet);

            return Content(String.Concat(doc.Declaration.ToString(), "\r\n", doc.ToString()), "text/xml");
        }
        return new HttpNotFoundResult("400");
    }
}