XML SelectSingleNode，其中同级='something'

Question

考虑以下XML:

<SomeRoot>
  <SomeElement>
    <SomeThing>25</SomeThing>
    <SomeOther>Cat</SomeOther>
  </SomeElement>
  <SomeElement>
    <SomeThing>46</SomeThing>
    <SomeOther>Dog</SomeOther>
  </SomeElement>
  <SomeElement>
    <SomeThing>83</SomeThing>
    <SomeOther>Bat</SomeOther>
  </SomeElement>
  <SomethingElse>Unrelated to the SomeElements above</SomethingElse>
</SomeRoot>

我想要select SomeThing where SomeOther = 'Cat'。以下C#代码抛出一个空引用异常：

xmlDoc = new XmlDocument();
this.path = path;
// Path is passed elsewhere
Console.WriteLine(xmlDoc.SelectSingleNode("/SomeRoot/SomeElement/SomeThing[../SomeOther='Cat']").InnerText);

此处使用的正确XPath语法是什么？

Answer 1

您缺少加载

var xmlDoc = new XmlDocument();
xmlDoc.Load(path);
Console.WriteLine(xmlDoc.SelectSingleNode("/SomeRoot/SomeElement/SomeThing[../SomeOther='Cat']").InnerText);

Answer 2

以下是我所做的事情，它是有效的；

XmlDocument xDoc = new XmlDocument();
xDoc.LoadXml(@"<SomeRoot><SomeElement><SomeThing>25</SomeThing><SomeOther>Cat</SomeOther></SomeElement></SomeRoot>");
var x = xDoc.SelectSingleNode("/SomeRoot/SomeElement/SomeThing[../SomeOther= 'Cat']").InnerText;

Answer 3

您可以避免使用任何反向轴：

/*/SomeElement[SomeOther='Cat']/SomeThing