XDocument.Element在解析xml字符串时返回null

Question

I have this xml string:

<a:feed xmlns:a="http://www.w3.org/2005/Atom" 
        xmlns:os="http://a9.com/-/spec/opensearch/1.1/"
        xmlns="http://schemas.zune.net/catalog/apps/2008/02">
    <a:link rel="self" type="application/atom+xml" href="/docs" />
    <a:updated>2014-02-12</a:updated>
    <a:title type="text">Chickens</a:title>
    <a:content type="html">eat 'em all</a:content>
    <sortTitle>Chickens</sortTitle>
    ... other stuffs
    <offers>
        <offer>
            <offerId>8977a259e5a3</offerId>
            ... other stuffs
            <price>0</price>
            ... other stuffs
        </offer>
    </offers>
    ... other stuffs
</a:feed>

and want to get value of <price> but here in my codes:

XDocument doc = XDocument.Parse(xmlString);
var a = doc.Element("a");
var offers = a.Element("offers");
foreach (var offer in offers.Descendants())
{
   var price = offer.Element("price");
   var value = price.Value;
}

doc.Element("a"); returns null. I tried removing that line offers is also null. what is wrong in my code and how to get value of price ? thanks

Answer 1

Here is correct way to get prices:

var xdoc = XDocument.Parse(xmlString);
XNamespace ns = xdoc.Root.GetDefaultNamespace();

var pricres = from o in xdoc.Root.Elements(ns + "offers").Elements(ns + "offer")
              select (int)o.Element(ns + "price");

Keep in mind that your document have default namespace, and a is also namespace.

Answer 2

Get the namespace somehow, like

XNameSpace a = doc.Root.GetDefaultNamespace();

or, probably better:

XNameSpace a = doc.Root.GetNamespaceOfPrefix("a");

and then use it in your queries:

// to get <a:feed>
XElement f = doc.Element(a + "feed");

You can also set the namespace from a literal string, but then avoid var .

Answer 3

var xDoc = XDocument.Load(filename);
XNamespace ns = "http://schemas.zune.net/catalog/apps/2008/02";
var prices = xDoc
                .Descendants(ns + "offer")
                .Select(o => (decimal)o.Element(ns + "price"))
                .ToList();

Answer 4

a is a namespace. To get the feed element try this:

XDocument doc = XDocument.Parse(xmlString);
XNamespace a = "http://www.w3.org/2005/Atom";
var feed = doc.Element(a + "feed");