title: Add namespace with colon to xml file
body: <p>I need to generate a xml file that looks like this:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;ns:Root xmlns:ns0="http://namespace"&gt;
    &lt;Node1&gt;
      &lt;A&gt;ValueA&lt;/A&gt;
      &lt;B&gt;ValueB&lt;/B&gt;
    &lt;/Node1&gt;
  &lt;/Root&gt;
  </code></pre>
  
  <p>This is my code:</p>
  
  <pre><code>const string ns = "http://namespace";
  var xDocument = new XDocument(
      new XElement("Root",
          new XAttribute(XNamespace.Xmlns + "ns0", ns),
          new XElement("Node1",
              new XElement("A", "ValueA"),
              new XElement("B", "ValueB")
          )
      )
  );
  </code></pre>
  
  <p>But this produces:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;Root xmlns:ns0="http://namespace"&gt;
    &lt;Node1&gt;
      &lt;A&gt;ValueA&lt;/A&gt;
      &lt;B&gt;ValueB&lt;/B&gt;
    &lt;/Node1&gt;
  &lt;/Root&gt;
  </code></pre>
  
  <p>Note the missing "ns0:" before the Root node. How can I add it? Everything else should be exactly the same.</p>