C# Select Node from XML by Attribute

Question

I need to be able to get the currency exchange rate from EUR => CHF for each day of a month. Therefor i got an XML Link from the gov.

The Link with the XML is this one.

Here's a snippet of the XML:

<devise code="eur">
  <land_de>Europäische Währungsunion</land_de>
  <land_fr>Union monétaire européenne</land_fr>
  <land_it>Unione Monetaria Europea</land_it>
  <land_en>Euro Member</land_en>
  <waehrung>1 EUR</waehrung>
  <kurs>1.05222</kurs>
</devise>
<devise code="gbp">
  <land_de>Grossbritannien</land_de>
  <land_fr>Grande-Bretagne</land_fr>
  <land_it>Gran Bretagna</land_it>
  <land_en>United Kingdom</land_en>
  <waehrung>1 GBP</waehrung>
  <kurs>1.48298</kurs>
</devise>

I need to get the value "1.05222" from the EUR node (which is the currency exchangerate).

I tried the following code, but it doesn't work, the result is always empty.

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(url);

string kurs="";

XmlNodeList xnList = xmlDoc.SelectNodes("/wechselkurse/devise[@code='eur']");
foreach (XmlNode xn in xnList)
{
   kurs = xn["kurs"].InnerText;
}

@CharlesMager: guess my memory was rusty.

Sam Axe
– Sam Axe

2015-08-13 09:41:09 +00:00
Commented Aug 13, 2015 at 9:41 — Sam Axe
– Sam Axe, Commented Aug 13, 2015 at 9:41

Charles Mager · Accepted Answer · 2015-08-13 09:38:18Z

3

I wouldn't use the old XmlDocument API. Here's how you might do it using the cleaner LINQ to XML API:

XNamespace ns = "http://www.afd.admin.ch/publicdb/newdb/mwst_kurse";

var doc = XDocument.Load("http://www.afd.admin.ch/publicdb/newdb/mwst_kurse/wechselkurse.php?d=20150701");

var eur = doc.Descendants(ns + "devise")
    .Where(e => (string)e.Attribute("code") == "eur")
    .Select(e => (decimal)e.Element(ns + "kurs"))
    .Single();

Here's a working demo: https://dotnetfiddle.net/Iz6NHO

You can also use XPath (though the query methods are usually preferable due to the static typing). The only issue with your query is you need to account for the namespace:

var nsm = new XmlNamespaceManager(new NameTable());

nsm.AddNamespace("k", "http://www.afd.admin.ch/publicdb/newdb/mwst_kurse");

var eur = (decimal)doc.XPathSelectElement("/k:wechselkurse/k:devise[@code='eur']/k:kurs", nsm);

edited Aug 13, 2015 at 9:38

answered Aug 13, 2015 at 9:29

Charles Mager

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