SyndicationFeed Class

            SyndicationFeed feed = new SyndicationFeed("Feed Title", "Feed Description", new Uri("http://Feed/Alternate/Link"), "FeedID", DateTime.Now);
            // Add a custom attribute.
            XmlQualifiedName xqName = new XmlQualifiedName("CustomAttribute");
            feed.AttributeExtensions.Add(xqName, "Value");

            SyndicationPerson sp = new SyndicationPerson("jesper@contoso.com", "Jesper Aaberg", "http://Jesper/Aaberg");
            feed.Authors.Add(sp);

            SyndicationCategory category = new SyndicationCategory("FeedCategory", "CategoryScheme", "CategoryLabel");
            feed.Categories.Add(category);

            feed.Contributors.Add(new SyndicationPerson("lene@contoso.com", "Lene Aaling", "http://lene/aaling"));
            feed.Copyright = new TextSyndicationContent("Copyright 2007");
            feed.Description = new TextSyndicationContent("This is a sample feed");

            // Add a custom element.
            XmlDocument doc = new XmlDocument();
            XmlElement feedElement = doc.CreateElement("CustomElement");
            feedElement.InnerText = "Some text";
            feed.ElementExtensions.Add(feedElement);

            feed.Generator = "Sample Code";
            feed.Id = "FeedID";
            feed.ImageUrl = new Uri("http://server/image.jpg");

            TextSyndicationContent textContent = new TextSyndicationContent("Some text content");
            SyndicationItem item = new SyndicationItem("Item Title", textContent, new Uri("http://server/items"), "ItemID", DateTime.Now);

            List<SyndicationItem> items = new List<SyndicationItem>();
            items.Add(item);
            feed.Items = items;

            feed.Language = "en-us";
            feed.LastUpdatedTime = DateTime.Now;

            SyndicationLink link = new SyndicationLink(new Uri("http://server/link"), "alternate", "Link Title", "text/html", 1000);
            feed.Links.Add(link);

            XmlWriter atomWriter = XmlWriter.Create("atom.xml");
            Atom10FeedFormatter atomFormatter = new Atom10FeedFormatter(feed);
            atomFormatter.WriteTo(atomWriter);
            atomWriter.Close();

            XmlWriter rssWriter = XmlWriter.Create("rss.xml");
            Rss20FeedFormatter rssFormatter = new Rss20FeedFormatter(feed);
            rssFormatter.WriteTo(rssWriter);
            rssWriter.Close();

<feed xml:lang="en-us" CustomAttribute="Value" xmlns="http://www.w3.org/2005/Atom">
  <title type="text">Feed Title</title>
  <subtitle type="text">This is a sample feed</subtitle>
  <id>FeedID</id>

  <rights type="text">Copyright 2007</rights>
  <updated>2007-04-13T17:29:38Z</updated>
  <category term="FeedCategory" label="CategoryLabel" scheme="CategoryScheme" />
  <logo>http://contoso/image.jpg</logo>
  <author>
    <name>Jesper Aaberg</name>
    <uri>http://contoso/Aaberg</uri>
    <email>Jesper.Asberg@contoso.com</email>
  </author>
  <contributor>
    <name>Lene Aalling</name>
    <uri>http://contoso/Aalling</uri>
    <email>Lene.Aaling@contoso.com</email>
  </contributor>
  <generator>Sample Code</generator>
  <link rel="alternate" type="text/html" title="Link Title" length="1000" href="http://contoso/link" />

  <link customAttribute="value" rel="alternate" type="text/html" title="Link Title" length="1000" href="http://contoso/link" />
  <CustomElement xmlns="">Some text</CustomElement>
  <entry>
    <id>ItemID</id>
    <title type="text">Item Title</title>
    <updated>2007-04-13T17:29:38Z</updated>
    <link rel="alternate" href="http://contoso/items" />
    <content type="text">Some text content</content>
  </entry>

</feed>

<rss xmlns:a10="http://www.w3.org/2005/Atom" version="2.0">
  <channel CustomAttribute="Value">
    <title>Feed Title</title>
    <link>http://feed/Alternate/Link</link>
    <description>This is a sample feed</description>
    <language>en-us</language>

    <copyright>Copyright 2007</copyright>

    <managingEditor>Jesper.Aaberg@contoso.com</managingEditor>
    <lastBuildDate>Fri, 13 Apr 2007 17:29:38 Z</lastBuildDate>
    <category domain="CategoryScheme">FeedCategory</category>
    <a10:link rel="alternate" type="text/html" title="Link Title" length="1000" href="http://contoso/link" />
    <generator>Sample Code</generator>

    <a10:contributor>
      <a10:name>Lene Aalling</a10:name>
      <a10:uri>http://contoso/Aalling</a10:uri>
      <a10:email>Lene.Aalling@contoso.com</a10:email>
    </a10:contributor>

    <a10:author>
      <a10:name>Lene Aalling</a10:name>
      <a10:uri>http://contoso/Aalling</a10:uri>
      <a10:email>Lene.Aalling@contoso.com</a10:email>
    </a10:author>
    <image>
      <url>http://contoso/image.jpg</url>
      <title>Feed Title</title>
      <link>http://feed/Alternate/Link</link>
    </image>
    <a10:id>FeedID</a10:id>
    <a10:link customAttribute="value" rel="alternate" type="text/html" title="Link Title" length="1000" href="http://contoso/link" />

    <CustomElement>Some text</CustomElement>
    <item>
      <guid isPermaLink="false">ItemID</guid>
      <link>http://contoso/items</link>
      <title>Item Title</title>
      <description>Some text content</description>
      <a10:updated>2007-04-13T17:29:38Z</a10:updated>
    </item>
  </channel>
</rss>