Question

我正在使用c＃来读取（尝试）RSS提要，但我收到错误"Namespace prefix 'cb' is not defined"，我对XML和C＃很陌生，并希望得到一些帮助，我读了一些关于创建命名空间，但我不是100％肯定我抓住了它。

非常感谢任何帮助。

C＃代码为：

 /*
      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);
        }
    }

，rss的摘要版本为：

<?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>

Answer 1

您需要在XmlNamespaceManager中添加“cb”才能在SelectSingleNode中使用“cb”。

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

XML名称空间前缀错误

1 个答案: