XPath + Namespace Driving me crazy

Question

Its a .vbproj and looks like this

<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"&gt;
    <PropertyGroup>
        <ProjectGuid>15a7ee82-9020-4fda-a7fb-85a61664692d</ProjectGuid>

all i want to get is the ProjectGuid but it does not work when a namespace i there...

 Dim xmlDoc As New XmlDocument()
 Dim filePath As String = Path.Combine(mDirectory, name + "\" + name + ".vbproj")
 xmlDoc.Load(filePath)
 Dim value As Object = xmlDoc.SelectNodes("/Project/PropertyGroup/ProjectGuid")

what can i do to fix this?

Answer 1

Why not use the // to ignore the namespace:

Dim value As Object = xmlDoc.SelectNodes("//ProjectGuid")

// acts as wild card to follow through everything between the root and the next node name specified(i.e ProjectGuid)

Answer 2

I'd probably be inclined to go with Bartek's* namespace solution, but a general xpath solution is:

//*[local-name()='ProjectGuid']

*since Bartek's answer has disappeared, I recommend Teun's (which is actually more thorough)

Answer 3

The best way to do things like this (IMHO) is to create a namespace manager. This can be used calling SelectNodes to indicate which namespace URLs are connected to which prefixes. I normally set up a static property that returns an adequate instance like this (it's C#, you'll have to translate):

private static XmlNamespaceManager _nsMgr;
public static XmlNamespaceManager NsMgr
{
  get
  {
    if (_nsMgr == null)
    {
      XmlDocument doc = new XmlDocument();
      _nsMgr = new XmlNamespaceManager(doc.NameTable);
      _nsMgr.AddNamespace("msb", "http://schemas.microsoft.com/developer/msbuild/2003");
    }
    return _nsMgr;
  }
}

I include only one namespace here, but you could have multiple. Then you can select from the document like this:

Dim value As Object = xmlDoc.SelectNodes("/msb:Project/msb:PropertyGroup/msb:ProjectGuid", NsMgr)

Note that all of the elements are in the specified namespace.

Answer 4

This problem has been here several times already.

Either you work with namspace-agnostic XPath expressions:

//*[local-name() = 'ProjectGuid']

or you use a XmlNamespaceManager and register the namespace so you can include a namespace prefix in you XPath:

Dim xmlDoc As New XmlDocument()
xmlDoc.Load(Path.Combine(mDirectory, name + "\" + name + ".vbproj"))          '"

Dim nsmgr As New XmlNamespaceManager(xmlDoc.NameTable)
nsmgr.AddNamespace("msb", "http://schemas.microsoft.com/developer/msbuild/2003")

Dim xpath As String = "/msb:Project/msb:PropertyGroup/msb:ProjectGuid"
Dim value As Object = xmlDoc.SelectNodes(xpath, nsmgr)

Answer 5

You need just to register this XML namespaces and associate with a prefix, to make the query work. Create and pass a namespace manager as second parameter when selecting the nodes:

Dim ns As New XmlNamespaceManager ( xmlDoc.NameTable )
ns.AddNamespace ( "msbuild", "http://schemas.microsoft.com/developer/msbuild/2003" )
Dim value As Object = xmlDoc.SelectNodes("/msbuild:Project/msbuild:PropertyGroup/msbuild:ProjectGuid", ns)