xml:lang not working in XPath expression

[manitoba]

Hi,

From C# I am trying to use an XPath expression with "xml:lang" in it but the compiler does not like it. Any idea how to do this in .NET?

XmlDocument doc = new XmlDocument();
doc.Load(@"C:\text.xml");
string test = doc.SelectSingleNode("/a/b[string(@xml:lang) = '']").InnerText();