Object Not Found Parsing XML

Question

I have the following XML being returned to me:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
  <document xmlns="@link" xmlns:xsi="@link" xsi:schemaLocation="@link" version="1.0">
    <field left="0" top="0" right="100" bottom="20" type="text">
      <value encoding="utf-16">11266</value>
      <line left="8" top="4" right="55" bottom="17">
        <char left="8" top="4" right="13" bottom="16" confidence="65" suspicious="true">1</char>
        <char left="18" top="4" right="23" bottom="16" confidence="68" suspicious="true">1</char>
        <char left="27" top="4" right="35" bottom="16" confidence="100">2</char><char left="36" top="4" right="45" bottom="17" confidence="100">6</char>
        <char left="46" top="4" right="55" bottom="16" confidence="100">6</char>
      </line>
   </field>
</document>

I'm trying to read the value node. My code looks like this:

Dim m_xmld = New XmlDocument()
m_xmld.Load(xmlfile) 
Return m_xmld.SelectSingleNode("/field/value").InnerText

What am I doing wrong? I tried /document/field/value as well to no avail :(

Answer 1

Try selecting the node from the root, like this:

Dim m_xmld = New XmlDocument()
m_xmld.Load(xmlfile) 

Return FindNode(m_xmld, "value")

Try using this function to search for the node:

Private Function FindNode(list As XmlNodeList, nodeName As String) As XmlNode
    If list.Count > 0 Then
        For Each node As XmlNode In list
            If node.Name.Equals(nodeName) Then
                Return node
            End If
            If node.HasChildNodes Then
                FindNode(node.ChildNodes, nodeName)
            End If
        Next
    End If

    Return Nothing
End Function

Answer 2

There are two problems with your code. First, you need to specify the XML namespace. The XML document contains a default namespace on the document element ( xmlns="@link" ). That means that you must explicitly specify that namespace when you reference any element in the document. To do that with XmlDocument , you need to create an XmlNamespaceManager and pass it to the select methods. For instance:

Dim m_xmld As New XmlDocument()
m_xmld.Load(xmlfile)
Dim nsmgr As New XmlNamespaceManager(m_xmld.NameTable)
nsmgr.AddNamespace("x", "@link")
return m_xmld.SelectSingleNode("/x:document/x:field/x:value", nsmgr).InnerText

Or, if you don't want to hard-code the namespace URI, you can just grab it from the loaded document, like this:

nsmgr.AddNamespace("x", m_xmld.DocumentElement.NamespaceURI)

The second problem is that you were trying to select /field/value rather than /document/field/value . When you are selecting from the XmlDocument object, itself, the selection begins from the root of the document ("above" the document element).