Linq to Xml and Namespace prefixes

Question

I am working with Linq to Xml to manipulate openXml documents. More precisely I am trying to read and write to the documents custom properties. I am currently having a problem appending a prefix onto an XElement. My code looks like:

Dim main as XNameSpace = "http://schemas.openxmlformats.org/officeDocument/2006/custom-properties"

Dim vt as XNameSpace = "http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"

Dim props as XElement = cXDoc.Element(main + "Properties"
        props.Add(New XElement(main + "property"), _
                               New XAttribute("fmtid", formatId), _
                               New XAttribute("pid", pid + 1), _
                               New XAttribute("name", "test"), _
                                    New XElement(vt + "lpwstr", "test value")) _
                 )

The Xml contained in props before the add is :

<Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes" />

The Xml after the props.add method() call is:

   <Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes"&gt;
  <property fmtid="{D5CDD505-2E9C-101B-9397-08002B2CF9AE}" pid="2" name="test">
    <lpwstr xmlns="http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"&gt;test value</lpwstr>
  </property>
</Properties>

Within the property element I should be getting

<vt:lpwstr>test value</vt:lpwstr>

but just can't get this to happen. I don't want the xmlns attribute for this element here either. I think I somehow need to get the map the vt XNameSpace back to the namespace declaration in the root element "Properties". Does anyone have any suggestions?

Answer 1

This page might point you in the right direction http://msdn.microsoft.com/en-us/library/bb387069.aspx

Answer 2

The way I have found to control where the namepaces are declared is to use Xml Literals. I also have to recreate the document from scratch and copy any existing information from the old document into my newly created document which isn't ideal. There is also a bug in the example above which is enough to get any of the Office Documents to corrupt after running the code.

Dim vt as XNameSpace = "http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"

Should read

Dim vt as XNameSpace = "http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes"

Answer 3

At some place in the XElement, you'll need the prefix defined. Here's how to do it by putting the vt xmlns at the top, by adding it as an XAttribute: New XAttribute(XNamespace.Xmlns + "vt", "http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes")

Dim main As XNamespace = "http://schemas.openxmlformats.org/officeDocument/2006/custom-properties"
Dim vt As XNamespace = "http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"
Dim formatId = "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}"
Dim pid = "2"
Dim props As New XElement(main + "Properties", New XAttribute(XNamespace.Xmlns + "vt", "http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"))
props.Add(New XElement(main + "property"), _
                       New XAttribute("fmtid", formatId), _
                       New XAttribute("pid", pid + 1), _
                       New XAttribute("name", "test"), _
                            New XElement(vt + "lpwstr", "test value"))

XML Literals and global namespaces may be easier, but you'll still need vt listed in the XML at a parent level. Here's an XML Literals example (remember to put both Imports statements at the top of the class/module, above everything else):

Imports <xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties"&gt;
Imports <xmlns:vt="http://schemas.openxmlformats.org/officeDocument2006/docPropsVTypes"&gt;
    Sub GetXml()
        Dim formatId = "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}"
        Dim pid = "2"
        Dim props2 = <Properties>
                         <property fmtid=<%= formatId %> pid=<%= pid + 1 %> name="test">
                             <vt:lpwstr>test value</vt:lpwstr>
                         </property>
                     </Properties>
        MsgBox(props2.ToString)
    End Sub