XPath and *.csproj

Look at the root namespace; you'll have to include an xml-namespace manager and use queries like "//x:ItemGroup", where "x" is your designated alias for the root namespace. And pass the manager into the query. For example:

        XmlDocument doc = new XmlDocument();
        doc.Load("my.csproj");

        XmlNamespaceManager mgr = new XmlNamespaceManager(doc.NameTable);
        mgr.AddNamespace("foo", doc.DocumentElement.NamespaceURI);
        XmlNode firstCompile = doc.SelectSingleNode("//foo:Compile", mgr);

You probably need to add a reference to the namespace http://schemas.microsoft.com/developer/msbuild/2003.

I had a similar problem, I wrote about it here. Do something like this:

XmlDocument xdDoc = new XmlDocument();
xdDoc.Load("blah/blah.csproj");

XmlNamespaceManager xnManager =
 new XmlNamespaceManager(xdDoc.NameTable);
xnManager.AddNamespace("tu",
 "http://schemas.microsoft.com/developer/msbuild/2003");

XmlNode xnRoot = xdDoc.DocumentElement;
XmlNodeList xnlPages = xnRoot.SelectNodes("//tu:ItemGroup", xnManager);