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我正在尝试遍历下面的 XML,并找到entry底层category元素具有collectionthrterm属性值的所有元素。以下示例中有 2 个。然后对于那些获取元素href属性的值。link但是,我似乎找不到正确的选择器:

<feed xmlns="http://www.w3.org/2005/Atom">
    <title>demo</title>
    <id>urn:uuid:071d9650-ae6c-11e7-8f1a-0800200c9a66</id>
    <link rel="self" href="https://test.com/atom/index.xml"/>
    <updated>2017-10-11T14:37:33+02:00</updated>
    <author>
        <name>Test</name>
        <uri>http://www.test.com</uri>
    </author>
    <generator version="1.8">Agent</generator>
    <entry>
        <title>YDEMO</title>
        <id>urn:uuid:15f44340-ae6c-11e7-8f1a-0800200c9a66</id>
        <category term="collection"/>
        <published>2017-10-11T13:41:53+02:00</published>
        <updated>2017-10-11T14:37:33+02:00</updated>
        <link rel="alternate" href="https://www.myurl.com" type="text/xml"/>
        <mcp:projectScenario xmlns:mcp="http://webservice.yes-co.nl/3mcp/1.5/atom-extension">NBvh</mcp:projectScenario>
    </entry>
    <entry>
        <title>DEMO 2</title>
        <id>urn:uuid:25f44340-ae6c-11e7-8f1a-0800200c9a00</id>
        <category term="collection"/>
        <published>2017-10-11T13:42:53+02:00</published>
        <updated>2017-10-11T14:38:33+02:00</updated>
        <link rel="alternate" href="https://www.myurl2.com" type="text/xml"/>
        <mcp:projectScenario xmlns:mcp="http://webservice.yes-co.nl/3mcp/1.5/atom-extension">BBvh</mcp:projectScenario>
    </entry>
    <entry>
        <title>photo</title>
        <id>12</id>
        <category term="metadata"/>
        <updated>2016-10-11T14:38:33+02:00</updated>
        <link rel="alternate" href="https://www.myurl2.com" type="text/xml"/>
    </entry>
    <entry
        xmlns:mcp="http://webservice.yes-co.nl/3mcp/1.5/atom-extension">
        <title>No title</title>
        <id>urn:uuid:6d65c57f-621f-4c15-8a1d-5dc967423d5d</id>
        <category term="media"/>
        <published>2017-10-11T13:39:43+02:00</published>
        <updated>2017-10-11T13:39:43+02:00</updated>
        <link
            xmlns:mcp="http://webservice.yes-co.nl/3mcp/1.5/atom-extension" rel="related" href="https://webservice.yes-co.com/3mcp/1.5/15f44340-ae6c-11e7-8f1a-0800200c9a66/media/6d65c57f-621f-4c15-8a1d-5dc967423d5d-large.jpg" type="image/jpg" mcp:mediaFormat="large"/>
    </entry>        
</feed>

到目前为止,这是我的代码,但即使data变量包含上面的 XML,该nodeList.Count行也会返回 0 个结果:

    Dim WC As New WebClient
    Dim data As String = WC.DownloadString("http://localhost/index.xml")

    Dim indexXML As New XmlDocument
    indexXML.LoadXml(data)

    Dim mgr As XmlNamespaceManager = New XmlNamespaceManager(indexXML.NameTable)
    mgr.AddNamespace("http://www.w3.org/2005/Atom", indexXML.DocumentElement.NamespaceURI)

    Dim node As XmlNode

    Dim root As XmlNode = indexXML.DocumentElement
    Dim nodeList As XmlNodeList = root.SelectNodes("/feed/entry")

    'now loop through all elements  with "category term=collection" in index.xml
    For i As Integer = 0 To nodeList.Count - 1
        If nodeList(i).SelectSingleNode("/category/@term=collection") IsNot Nothing Then
            LogMessage(nodeList(i).SelectSingleNode("/category/link/@href").Value)
        End If
    Next i  

更新 1
我想选择所有具有类别节点的“条目”元素term=collection。该部分通过以下语句起作用:indexXML.SelectNodes("/atom:feed/atom:entry[atom:category/@term=""collection""]", mgr)

我想从入口节点开始,然后我想选择入口的子元素链接的 href 属性(以及将来的其他子元素entry。但是,我在下面尝试的示例都没有返回href属性的值。如何我可以解决吗?

我现在有这个:

Dim mgr As XmlNamespaceManager = New XmlNamespaceManager(indexXML.NameTable)
mgr.AddNamespace("atom", "http://www.w3.org/2005/Atom")

Dim root As XmlNode = indexXML.DocumentElement
Dim nodeList As XmlNodeList = indexXML.SelectNodes("/atom:feed/atom:entry[atom:category/@term=""collection""]", mgr)

'now loop through all collections in index.xml

For i As Integer = 0 To nodeList.Count - 1 '1 result found

'NONE OF CALLS BELOW RETURN THE VALUE OF HREF ATTRIBUTE
    If nodeList(i).SelectSingleNode("atom:/link/@href", mgr) IsNot Nothing Then
        LogMessage(nodeList(i).SelectSingleNode("atom:/link/@href", mgr).Value)
'error: 'atom:/link/@href' has an invalid qualified name.
    End If
Next i

更新 2 感谢@Pawel,我能够选择所有entry节点作为节点属性的project值,如下所示:termcategory

objectsXML.SelectNodes("/atom:feed/atom:entry[atom:category/@term=""project""]", mgr)

但是,如何向此选择器添加额外的标准以过滤掉entry具有值NBvhORBBvh的节点mcp:projectScenario

更新 3 我向管理器添加了一个额外的命名空间:

mgr.AddNamespace("atom", "http://www.w3.org/2005/Atom")
mgr.AddNamespace("mcp", "http://webservice.yes-co.nl/3mcp/1.5/atom-extension")

但是当我尝试href通过 uuid 选择媒体元素的属性时,我得到了错误:Object reference not set to an instance of an object.

我的代码:

objectsXML.SelectSingleNode("/atom:feed/atom:entry[atom:id=""urn:uuid:" + "6d65c57f-621f-4c15-8a1d-5dc967423d5d" + """]/mcp:link/@href", mgr).InnerText
4

1 回答 1

1

该文档使用http://www.w3.org/2005/Atom命名空间。您需要将此命名空间绑定到 uri 前缀并在 XPath 中使用此前缀。如果将命名空间绑定到atom前缀,如下所示:

var nsmanager = new XmlNamespaceManager(indexXML.NameTable);
nsmanager.AddNamespace("atom", "http://www.w3.org/2005/Atom");

如果您传递命名空间管理器,您将能够在 XPath 表达式中使用此前缀,例如:

indexXML.SelectNodes("/atom:feed/atom:entry[atom:category/@term="collection"]/atom:link/@href", nsmanager)
于 2017-11-04T02:41:44.147 回答