Unexpected handling of XML namespace between original object and XML from its saved file

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After creating a XmlDocument object and creating XML, I can use the .SelectNodes method to get back the nodes from the original object by not prefixing the node names with the namespace prefix. I get nothing if I use the prefix. However when I save the XML document, and reload it. I get the reverse effect. Not using the prefix returns nothing while using the prefix gets results. Can anyone help me understanding here and suggest the correct way.

I have attached some test code here in VB;

Dim Root As XmlElement = Xdoc.DocumentElement
 Dim xmldecl As XmlDeclaration
 xmldecl = Xdoc.CreateXmlDeclaration("1.0", "UTF-8", Nothing)
 Xdoc.InsertBefore(xmldecl, Root)

 Dim BooksNode As XmlNode
 BooksNode = Xdoc.CreateNode(XmlNodeType.Element, "Books", "")
 Dim Attrib As XmlAttribute = Xdoc.CreateAttribute("xmlns")
 Attrib.Value = "http://www.Company.com.au/xml"
 BooksNode.Attributes.Append(Attrib)
 Xdoc.AppendChild(BooksNode)

 Dim BookNode As XmlNode
 BookNode = Xdoc.CreateNode(XmlNodeType.Element, "Book", "")
 BookNode.InnerText = ""
 BooksNode.AppendChild(BookNode)

 Dim BookNameNode As XmlNode
 BookNameNode = Xdoc.CreateNode(XmlNodeType.Element, "BookName", "")
 BookNameNode.InnerText = "Hitchhikers guide to the galaxy"
 BookNode.AppendChild(BookNameNode)

 Dim BookNode2 As XmlNode
 BookNode2 = Xdoc.CreateNode(XmlNodeType.Element, "Book", "")
 BookNode2.InnerText = ""
 BooksNode.AppendChild(BookNode2)

 Dim BookNameNode2 As XmlNode
 BookNameNode2 = Xdoc.CreateNode(XmlNodeType.Element, "BookName", "")
 BookNameNode2.InnerText = "The Power of one"
 BookNode2.AppendChild(BookNameNode2)

 Dim NsMgr As New XmlNamespaceManager(Xdoc.NameTable)
 NsMgr.AddNamespace("bk", "http://www.Company.com.au/xml")

 Dim BooksNoNsPrefix = Xdoc.SelectNodes("/Books/Book", NsMgr)
 Debug.Print("No Namespace prefix:" & BooksNoNsPrefix.Count.ToString)

 Dim BooksNsPrefix = Xdoc.SelectNodes("/bk:Books/bk:Book", NsMgr)
 Debug.Print("Using Namespace prefix:" & BooksNsPrefix.Count.ToString)

 Xdoc.Save("C:\Temp\Test.xml")
 Dim NewXdox As New XmlDocument
 NewXdox.Load("C:\Temp\Test.xml")

 Dim NsMgr2 As New XmlNamespaceManager(NewXdox.NameTable)
 NsMgr2.AddNamespace("bk", "http://www.Company.com.au/xml")

 Dim BooksNoNs2 = NewXdox.SelectNodes("/Books/Book", NsMgr2)
 Debug.Print("No Namespace prefix:" & BooksNoNs2.Count.ToString)

 Dim BooksNs2 = NewXdox.SelectNodes("/bk:Books/bk:Book", NsMgr2)
 Debug.Print("Using Namespace prefix:" & BooksNs2.Count.ToString)

The Output is;

No Namespace prefix : 2
Using Namespace prefix : 0
No Namespace prefix : 0
Using Namespace prefix : 2

Posted 28-Oct-13 18:00pm

Coding123456

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PIEBALDconsult 29-Oct-13 0:35am

XML namespaces are rather tricky and I've had a bit of trouble working with them.
One thing I would cauthion is not to use the default (empty) namespace.
It looks like what you have should work. Can you add a snippet of the generated XML?

Come to think of it, I suppose the Attribute you create doesn't get interpreted as a namespace until it's read in -- that could be the issue, but I don't know the solution.

Coding123456 12-Nov-13 20:11pm

Thanks for your reply PEIBALDconsult, You were on the right track.

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woopsydoozy · Accepted Answer · 2013-10-30T07:11:00

It's because you're not adding your namespace as you should. Rather than add it as an attribute after you create a node, add it as the namespace when you create the node:

VB

Dim xdoc As New XmlDocument
Dim Root As XmlElement = Xdoc.DocumentElement
Dim xmldecl As XmlDeclaration
xmldecl = xdoc.CreateXmlDeclaration("1.0", "UTF-8", Nothing)
Xdoc.InsertBefore(xmldecl, Root)

Dim BooksNode As XmlNode
Dim ns As String = "http://www.Company.com.au/xml"
BooksNode = xdoc.CreateNode(XmlNodeType.Element, "Books", ns)
xdoc.AppendChild(BooksNode)

Dim BookNode As XmlNode
BookNode = xdoc.CreateNode(XmlNodeType.Element, "Book", ns)
BookNode.InnerText = ""
BooksNode.AppendChild(BookNode)

Dim BookNameNode As XmlNode
BookNameNode = xdoc.CreateNode(XmlNodeType.Element, "BookName", ns)
BookNameNode.InnerText = "Hitchhikers guide to the galaxy"
BookNode.AppendChild(BookNameNode)

Dim BookNode2 As XmlNode
BookNode2 = xdoc.CreateNode(XmlNodeType.Element, "Book", ns)
BookNode2.InnerText = ""
BooksNode.AppendChild(BookNode2)

Dim BookNameNode2 As XmlNode
BookNameNode2 = xdoc.CreateNode(XmlNodeType.Element, "BookName", ns)
BookNameNode2.InnerText = "The Power of one"
BookNode2.AppendChild(BookNameNode2)

Dim NsMgr As New XmlNamespaceManager(xdoc.NameTable)
NsMgr.AddNamespace("bk", "http://www.Company.com.au/xml")
NsMgr.PushScope()

Dim BooksNoNsPrefix = Xdoc.SelectNodes("/Books/Book", NsMgr)
Debug.Print("No Namespace prefix:" & BooksNoNsPrefix.Count.ToString)

Dim BooksNsPrefix = Xdoc.SelectNodes("/bk:Books/bk:Book", NsMgr)
Debug.Print("Using Namespace prefix:" & BooksNsPrefix.Count.ToString)

Xdoc.Save("C:\Temp\Test.xml")
Dim NewXdox As New XmlDocument
NewXdox.Load("C:\Temp\Test.xml")

Dim NsMgr2 As New XmlNamespaceManager(NewXdox.NameTable)
NsMgr2.AddNamespace("bk", "http://www.Company.com.au/xml")

Dim BooksNoNs2 = NewXdox.SelectNodes("/Books/Book", NsMgr2)
Debug.Print("No Namespace prefix:" & BooksNoNs2.Count.ToString)

Dim BooksNs2 = NewXdox.SelectNodes("/bk:Books/bk:Book", NsMgr2)
Debug.Print("Using Namespace prefix:" & BooksNs2.Count.ToString)