title: Reading an attribute through XPath in xml document does not work
body: <p>I have a simple xml document below:</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;Research researchID="RT_a" language="eng" xmlns="http://www.rixml.org/2010/1/RIXML" createDateTime="2012-06-30T01:13:38Z"&gt;
    &lt;Product productID="RT_a"&gt;
                &lt;SecurityID idType="ISIN" idValue="US0605051046" /&gt;
    &lt;/Product&gt;
  &lt;/Research&gt;
  </code></pre>
  
  <p>I am trying to read an attribute "idValue" with the give XPath string. This does not work unless I remove this part:</p>
  
  <pre><code>xmlns="http://www.rixml.org/2010/1/RIXML" 
  </code></pre>
  
  <p>My code is below:</p>
  
  <pre><code>    Dim doc As XPathDocument = New XPathDocument("c:\test\test.xml")
  
      Dim strXPath As String = "/Research[1]/Product[1]/SecurityID[1]"
      Dim nav As XPathNavigator = doc.CreateNavigator()
      Dim mgr As New XmlNamespaceManager(nav.NameTable)
  
      mgr.AddNamespace("", "http://www.rixml.org/2010/1/RIXML")
  
      Dim XPathNode As XPathNavigator = nav.SelectSingleNode(strXPath, mgr)
      If XPathNode IsNot Nothing Then
          Console.WriteLine(XPathNode.GetAttribute("idValue", String.Empty))
      Else
          Console.WriteLine("Nothing found")
      End If
  </code></pre>
  
  <p>The row about adding name space have no effect on result - just did some tests with that. What do I need to do/what am I doing wrong?</p>