using XElement to query for a node in namespace

Question

i'm trying to pull out a node from a csproj file that looks like this, but can't get it to work - presumably because of the namespace declaration.

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="Build">
      <PropertyGroup>
          <RegisterForComInterop>true</RegisterForComInterop>

This fails miserably:

XDocument cpo = XDocument.Load(file);
XmlNamespaceManager nsm = new XmlNamespaceManager(new NameTable());
nsm.AddNamespace("x", "http://schemas.microsoft.com/developer/msbuild/200");
IEnumerable<XElement> list3 = cpo.XPathSelectElements("//x:RegisterForComInterop[.='true']", nsm);

Anyone any ideas please?

Thanks.

Answer 1

Do you really want to use XPath for this? It's really easy to use namespaces within LINQ to XML:

XDocument cpo = XDocument.Load(file);
XNamespace x = "http://schemas.microsoft.com/developer/msbuild/2003";
var elements = cpo.Descendants(x + "RegisterForComInterop")
                  .Where(x => (string) x == "true");

or if you're absolutely convinced that every RegisterForComInterop will have an appropriate Boolean value you can use the explicit XElement to bool conversion:

XDocument cpo = XDocument.Load(file);
XNamespace x = "http://schemas.microsoft.com/developer/msbuild/2003";
var elements = cpo.Descendants(x + "RegisterForComInterop")
                  .Where(x => (bool) x);

Personally I would usually go this route rather than XPath especially if namespaces are involved.