抛出异常:需要命名空间管理器或 XsltContext [英] Throw an exception: Namespace Manager or XsltContext needed

问题描述

我问了一个关于使用 XPath 函数的问题 那里

I ask a question about using XPath function there

但是我遇到了一个关于这个异常的问题:

But I meet a problem about this exception:

[System.Xml.XPath.XPathException] = {"Namespace Manager or XsltContext needed. This query has a prefix, variable, or user-defined function."}

xml如下:

<x-config>
    <!--user location-->
    <x-list>
      <Country code="TW,UK,MY" />
      <Country code="US,CA,MX" />
      <Country code="IN,PR,VI,IR" />
      <Country code="Others" /> 
    </x-list>

我使用以下代码来检索匹配项:

And I use following code to retrieve matches:

XmlNode countryNode = cdnConfig.SelectSingleNode(
    string.Format("x-config/x-list/Country[fn:contains(@code, {0})]", countryCode)
);

我是 XPath 的新手.有人可以详细说明这一点并提供一些解决方法吗?

I am a newbie of XPath. Could anybody elaborate more on this and give some workaround?

非常感谢.

推荐答案

这个问题应该回答

简而言之:无法识别 XPath 表达式中的 fn 前缀.您可以提供一个 XmlNamespaceManager 实例来声明前缀，但由于 .NET 显然没有 XPath 2.0 支持，因此这无济于事.

In short: The fn prefix in your XPath expression is not recognized. You could supply an instance of XmlNamespaceManager to declare the prefix, but since .NET apparently doesn't have XPath 2.0 support, this won't help.

然而，contains 函数已经被 XPath 1.0 支持，所以不需要 XPath 2.0:

However, the contains function is already supported by XPath 1.0, so no need for XPath 2.0:

XmlNode countryNode = cdnConfig.SelectSingleNode(
    string.Format("x-config/x-list/Country[contains(@code, '{0}')]", countryCode)
);                                         ↑

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