XML namespace prefix error

Question

I am using c# to read (attempting to) an RSS feed, but I am getting an error "Namespace prefix 'cb' is not defined" , I am pretty new to XML and C# and was hoping for some help, I read a bit on creating the Namespace but I am not 100% sure I am grasping it.

Any help would be greatly appreciated.

The C# code is:

 /*
      Add rows by calling the AddRow method on the member variable named "<Output Name>Buffer".
      For example, call MyOutputBuffer.AddRow() if your output was named "MyOutput".
    */
    // Create an XmlNamespaceManager to resolve the default namespace.

    XmlDocument xm = new XmlDocument();
    xm.Load(Variables.USFeed.ToString());
    XmlNamespaceManager nsmgr = new XmlNamespaceManager(xm.NameTable);
    nsmgr.AddNamespace("rdf", "http://purl.org/rss/1.0/");
    XmlNodeList xnode = xm.GetElementsByTagName("item");


    foreach (XmlNode xmn in xnode)
    {            
        XmlElement currencyElement = (XmlElement)xmn;
        if (currencyElement.HasAttribute("rdf:about"))
        {
            Output0Buffer.AddRow();
            Output0Buffer.observationPeriod = currencyElement.SelectSingleNode("cb:statistics/cb:exchangeRate/cb:observationPeriod", nsmgr).InnerText;
            Output0Buffer.targetCurrency = currencyElement.SelectSingleNode("cb:statistics/cb:exchangeRate/cb:targetCurrency", nsmgr).InnerText;
            Output0Buffer.baseCurrency = currencyElement.SelectSingleNode("cb:statistics/cb:exchangeRate/cb:baseCurrency", nsmgr).InnerText;
            Output0Buffer.exchangeRate = double.Parse(currencyElement.SelectSingleNode("cb:statistics/cb:exchangeRate/cb:value", nsmgr).InnerText);
        }
    }

and the summarized version of the rss is:

<?xml version="1.0" encoding="ISO-8859-1"?>
<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns="http://purl.org/rss/1.0/"
    xmlns:cb="http://www.cbwiki.net/wiki/index.php/Specification_1.1"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:dcterms="http://purl.org/dc/terms/"
    xmlns:xsi="http://www.w3c.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.w3c.org/1999/02/22-rdf-syntax-ns#rdf.xsd">
    <channel rdf:about="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_ALL.xml">
        <title xml:lang="en">Bank of Canada: Noon Foreign Exchange Rates</title>
        <link>http://www.bankofcanada.ca/rates/exchange/noon-rates-5-day/</link>
        <description>Current day's noon foreign exchange rates from the Bank of Canada. Published at about 12:15 ET.</description>
        <items>
            <rdf:Seq>
                <rdf:li rdf:resource="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_USD.xml" /> 
                <rdf:li rdf:resource="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_VEF.xml" /> 
<rdf:li rdf:resource="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_VND.xml" /> 
            </rdf:Seq>
        </items>
    </channel>
    <item rdf:about="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_USD.xml">
        <title xml:lang="en">CA: 0.9382 USD = 1 CAD 2014-01-06 Bank of Canada noon rate</title>
        <cb:statistics>
            <cb:country>CA</cb:country>
            <cb:exchangeRate>
                <cb:value decimals="4">0.9382</cb:value>
                <cb:baseCurrency>CAD</cb:baseCurrency>
                <cb:targetCurrency>USD</cb:targetCurrency>
                <cb:rateType>Bank of Canada noon rate</cb:rateType>
                <cb:observationPeriod frequency="daily">2014-01-06T12:15:00-05:00</cb:observationPeriod>
            </cb:exchangeRate>
        </cb:statistics>
    </item>
    <item rdf:about="http://www.bankofcanada.ca/stats/assets/rates_rss/noon/en_ARS.xml">
        <title xml:lang="en">CA: 6.1843 ARS = 1 CAD 2014-01-06 Bank of Canada noon rate</title>
        <cb:statistics>
            <cb:country>CA</cb:country>
            <cb:exchangeRate>
                <cb:value decimals="4">6.1843</cb:value>
                <cb:baseCurrency>CAD</cb:baseCurrency>
                <cb:targetCurrency>ARS</cb:targetCurrency>
                <cb:rateType>Bank of Canada noon rate</cb:rateType>
                <cb:observationPeriod frequency="daily">2014-01-06T12:15:00-05:00</cb:observationPeriod>
            </cb:exchangeRate>
        </cb:statistics>
    </item>

Why have you decided to use old-style XmlDocument? It would be much easier with XDocument and LINQ to XML :) — MarcinJuraszek
– MarcinJuraszek, Commented Jan 8, 2014 at 19:38
The only reason is because I was looking for an RSS to SSIS example and this is what popped up as an example, beyondrelational.com/modules/24/syndicated/398/Posts/9954/… heh — jnoel10
– jnoel10, Commented Jan 8, 2014 at 19:50

Michael Gunter · Accepted Answer · 2014-01-08 19:45:27Z

4

You need to add "cb" to your XmlNamespaceManager in order to use "cb" in SelectSingleNode.

nsmgr.AddNamespace(
    "cb", 
    "http://www.cbwiki.net/wiki/index.php/Specification_1.1");

edited Jan 8, 2014 at 19:45

answered Jan 8, 2014 at 19:37

Michael Gunter

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5 Comments

Michael Gunter Over a year ago

Also, I would recommend that you use currencyElement.HasAttribute("about", "http://www.w3.org/1999/02/22-rdf-syntax-ns#") instead of currencyElement.HasAttribute("rdf:about")

jnoel10 Over a year ago

It worked perfectly, thank you. I did not know i could add multiple namespaces.

jnoel10 Over a year ago

I changed the HasAttribute as well, and that also works.. however I don't understand why it works. since the www.w3.org is referencing the cb and not the rdf:

Michael Gunter Over a year ago

You've got it backwards. "cb" is referencing "http://www.cbwiki.net/wiki/index.php/Specification_1.1" and "rdf" is referencing "http://www.w3.org/1999/02/22-rdf-syntax-ns#".

jnoel10 Over a year ago

ahh, that would be why.. sorry long day. Thanks again for your help

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