Question

i am trying to select “description” from a rss feed if the title is equal to something.

in code i have this :

public static XmlDocument GetDefaultHoroscopesFeed(string StarSign){
 xdoc.SelectSingleNode(string.Format("rss/channel/item/[title = '{0}']/description", StarSign));
            xdoc.LoadXml(DefaultPageHoroscopeNode.InnerXml);
            return xdoc;

}

but i keep getting this error : Expression must evaluate to a node-set.

Please help someone

Answer 1

You’re not specifying a node name inbetween .../item/ and [title = ..., therefore you won’t get back a valid node-set. Also, in RSS, the <title> node will not have a child node called <description>.

You need to change your XPath

"rss/channel/item/[title = '{0}']/description"

into

"rss/channel/item[title = '{0}']/description"

This will get you the <item> node that has a <title> node with the value StarSign and then retrieve its <description> node.

You could also do this using an XDocument and Linq to XML, like so:

XDocument xdoc = XDocument.Load(pathToRss);
XElement description = xdoc.Descendants("item")
    .Where(i => i.Element("title").Value.Equals(StarSign))
    .Select(i => i.Element("description"))
    .FirstOrDefault();