无法使用 XmlDocument.select 节点选择节点

Question

我尝试使用 XmlDocument.select 在下面的 xml 文件中获取节点的值

<?xml version="1.0"?>
<cqresponse xmlns="http://ibm.com/rational/clearquest/web/v7.1">
  <displayname>hello world</displayname>
  <fields>
    <field>
      <fieldname>Defect_details_linenumber</fieldname>
      <datatype>MULTILINE_STRING</datatype>
      <value><![CDATA[["aaa"]]]></value>
    </field>
    <field>
      <fieldname>Defect_detailsAf_artefs</fieldname>
      <datatype>MULTILINE_STRING</datatype>
      <value><![CDATA[["bbb"]]]></value>
    </field>
  </fields>
</cqresponse>

使用此代码

Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click     
    Dim doc As XmlDocument = New XmlDocument()
    doc.Load("Temp_File.xml")
    Dim nodeList As XmlNodeList
    Dim root As XmlNode = doc.DocumentElement
    nodeList = root.SelectNodes("descendant::fields[field/fieldname='Defect_detailsAf_artefs']")

    Debug.Print(nodeList.Count)
    Debug.Print(nodeList(0).InnerText)
End Sub

但 nodelist.count 总是返回 0。我认为它找不到节点“Defect_details_linenumber”。您能否帮我指出 xPath "descendant::fields[field/fieldname='Defect_detailsAf_artefs']" 中是否有问题或代码中有问题

我尝试使用 xpath ""descendant::fields" 但我遇到了同样的问题 nodelist.count 仍然返回 0

已解决

无法选择节点，因为它缺少命名空间。如果我们改为这样，我的代码会很好

Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click     
    Dim doc As XmlDocument = New XmlDocument()
    doc.Load("Temp_File.xml")

    'Add namespace for xml here
    Dim ns As XmlNamespaceManager = New XmlNamespaceManager(doc.NameTable)
    ns.AddNamespace("ibm", "http://ibm.com/rational/clearquest/web/v7.1")

    'Get root node: node "cqresponse"
    Dim root As XmlNode = doc.DocumentElement
    'Get node which have child node fieldname = 'Defect_details_linenumber'
    Dim node As XmlNode = root.SelectSingleNode("descendant::ibm:fields/ibm:field[ibm:fieldname='Defect_detailsAf_artefs']/ibm:value", ns)

    Debug.Print(node.InnerText) 'it will show "bbb"

End Sub

Answer 1

这是因为 XML 在根目录中声明了 默认命名空间。这意味着该 XML 文档中所有没有前缀的元素都在命名空间 http://ibm.com/rational/clearquest/web/v7.1 中。为了能够使用 XPath 选择命名空间中的元素，您需要定义一个引用该命名空间的前缀，并修改 XPath 以使用该前缀，例如：

....
Dim nsManager As New XmlNamespaceManager(New NameTable())
nsManager.AddNamespace("d", "http://ibm.com/rational/clearquest/web/v7.1")
nodeList = root.SelectNodes("//d:fields[d:field/d:fieldname='Defect_detailsAf_artefs']", nsManager)

Answer 2

Imports <xmlns="http://ibm.com/rational/clearquest/web/v7.1">

Sub Test()
    Dim xml =
        <?xml version="1.0"?>
        <cqresponse xmlns="http://ibm.com/rational/clearquest/web/v7.1">
            <displayname>hello world</displayname>
            <fields>
                <field>
                    <fieldname>Defect_details_linenumber</fieldname>
                    <datatype>MULTILINE_STRING</datatype>
                    <value><![CDATA[["aaa"]]]></value>
                </field>
                <field>
                    <fieldname>Defect_detailsAf_artefs</fieldname>
                    <datatype>MULTILINE_STRING</datatype>
                    <value><![CDATA[["bbb"]]]></value>
                </field>
            </fields>
        </cqresponse>

    Dim fields = xml...<field>.Where(Function(f) f.<fieldname>.Value = "Defect_detailsAf_artefs")
    fields.ToList().ForEach(Sub(f) Console.WriteLine(f.ToString()))
End Sub