Unable access elements inside Xelement directly

Question

I have this XML inside an Xelement object called request:

    <?xml version="1.0" encoding="UTF-8"?>
<Message xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:nc="http://niem.gov/niem/niem-core/2.0">
    <List>
        <nc:Title/>
        <nc:Text/>
        <nc:Value/>
        <nc:ID>1234567890</nc:ID>
    </List>
</Message>

I can reach the value of the ID element by using:

request.Elements().Where(Function(e) e.Name.LocalName = "List").Value

However, this concatenates all the values of the elements inside the <List> element. According to what I have read, I should be able to get the value of an element by:

request.Element("ID")

...But I think the namespaces interfere. I am unable to directly query any of the four elements nested inside the List element. I have read several posts and tried several variations, but have had no luck. Please help :)

Example of reading xml into xelement and querying for ID which returns a value of Nothing:

 Dim tester As XElement = XElement.Load("C:\test.xml")
 Dim value As String = tester.Elements.Where(Function(e) e.Name.LocalName = "ID").Value

Show what's hidden under `...all my namespaces` and an example of query that is not working. — MarcinJuraszek, Aug 20 '13 at 19:30

score 1 · Accepted Answer · answered Aug 21 '13 at 14:34

1

You have to use XNamespace instance:

Dim doc = XDocument.Load("Input.txt")
Dim nc = XNamespace.Get("http://niem.gov/niem/niem-core/2.0")

Dim value = doc.Root.Element("List").Element(nc + "ID")

answered Aug 21 '13 at 14:34

MarcinJuraszek

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Thanks, this works, I had tried something similar, but must have been using the wrong namespace class. I also found that the Descendants method gives me a deeper level granularity into my Xelement, so I can also get the values of elements by: `Dim value As String = tester.Descendants.Where(Function(e) e.Name.LocalName = "ID")` – Popo Aug 21 '13 at 17:50
@Sanpopo `Descendants` performs traverse deep down the document tree, so it almost always checks a lot of unnecessary items. That's why you should use `Element`/`Elements` instead - it will be faster. – MarcinJuraszek Aug 21 '13 at 18:04

score 0 · Answer 2 · answered Aug 20 '13 at 20:37

0

It is necessary to use XmlNamespaceManager. Let's suppose that your xml is in myfile.xml. Name spaces are missing in your code so I used Microsoft ones instead.

Dim reader As New XmlTextReader("myfile.xml")
Dim doc As New XmlDocument()
doc.Load(reader)
Dim nsmanager As New XmlNamespaceManager(doc.NameTable)
nsmanager.AddNamespace("nc", "www.microsoft.com/books")
nsmanager.AddNamespace("default", "www.microsoft.com/store")
Dim book as XmlNode 
Dim root as XmlElement = doc.DocumentElement
book = root.SelectSingleNode("//nc:ID", nsmanager)

Code is built from MS samples and was never run. Please apologize mistakes.
For more information see:
Manage Namespaces Using the XmlNamespaceManager
XmlNode.SelectSingleNode

answered Aug 20 '13 at 20:37

IvanH

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Do I need to do this if I am using an Xelement object? – Popo Aug 21 '13 at 13:07
If you need XPath (I am not sure) and you have namespaces you cannot get out wihout XmlNamespaceManager. Otherwise please specify more clearly what do you mean by "access elements". – IvanH Aug 21 '13 at 13:13
Access/obtain the value inside the element. – Popo Aug 21 '13 at 17:45

Unable access elements inside Xelement directly

2 Answers2