How to select particular node from XML

Question

I have this XML:

<?xml version="1.0"?>
    <Document xmlns="urn:somethinghere">
        <fapx.001.02>
            <Sts>
                <StsVal>ACCEPTED</StsVal>
            </Sts>
        </fapx.001.02>
    </Document>

I want to select value of "StsVal" and for that I wrote this code but getting error:

Code

Dim doc As XmlDocument = New XmlDocument()
doc.Load("myfile.xml")
Dim response As String = doc.SelectSingleNode("Document/fapx.001.02/Sts/StsVal").InnerText

Error

Object reference not set to an instance of an object.

EDIT

I know I am getting this error due to Nulll value probably because the path I have given in SelectSingleNode function is not correct. That's why I want to know how to give correct path based on given XML.

Related: [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Bjørn-Roger Kringsjå, Nov 22 '15 at 08:30
@Bjørn-RogerKringsjå I know it is because of Null value because what I don't know how to select that particular node based on the given XML. — Frank Martin, Nov 22 '15 at 08:31
You should **(1)** check if the `doc` is NULL after you've called `doc.Load()` (just to be sure the loading from the file has actually worked), then **(2)** you should use the call to `.SelectSingleNode()` and get the result of that call into a variable and then also check for NULL before accessing its `.InnerText` property.... — marc_s, Nov 22 '15 at 09:03

score 2 · Accepted Answer · edited May 23 '17 at 10:27

That's because your XML has default namespace : xmlns="urn:somethinghere". This topic (XPath query against XML with default namespace) has been asked so many times previously in various forms here in SO. Here are some from my answer history :

And this is one possible way to query element in namespace using XPath and XmlDocument :

Dim nsManager As New XmlNamespaceManager(New NameTable())
nsManager.AddNamespace("d", "urn:somethinghere")

Dim doc As XmlDocument = New XmlDocument()
doc.Load("myfile.xml")
Dim response As String = doc.SelectSingleNode("d:Document/d:fapx.001.02/d:Sts/d:StsVal", nsManager).InnerText

score 2 · Answer 2 · answered Nov 22 '15 at 09:02

Your problem is that your document has a default namespace, but the XPath expression doesn't use it. You can pass in a namespace manager and use an alias for the namespace like this:

Dim xnm as XmlNamespaceManager = New XmlNamespaceManager( doc.NameTable )
xnm.AddNamespace("ns", "urn:somethinghere")
Dim response As String = doc.SelectSingleNode("ns:Document/ns:fapx.001.02/ns:Sts/ns:StsVal", xnm).InnerText

My vb's a little rusty, apologies if the syntax needs a little adjustment, but hopefully you get the idea. The "ns" is abritrary, you can use anything you want as a temporary prefix.

It feels like there should be a way of getting it to recognize the default namespace, but for some reason adding the documents nametable on it's own doesn't seem to recognize it, but giving it a name will work.

How to select particular node from XML

2 Answers2

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