title: insert XmlDocument into a XmlDocument node
body: <p>I created a basic XmlDocument with one node:</p>
  
  <pre><code>XmlDocument bigDoc = new XmlDocument();
  bigDoc.LoadXml("&lt;Request&gt;&lt;/Request&gt;");
  </code></pre>
  
  <p>and I'm getting another XmlDocument that I want to insert inside <code>&lt;Request&gt;</code> node.
  It doesn't work for me:</p>
  
  <pre><code> XmlNode requestNode =  bigDoc.FirstChild;
   requestNode.AppendChild(anotherXMLDocument);
  </code></pre>
  
  <p>It thorows an exception.</p>
  
  <p>How can I insert a XmlDocument inside another XmlDocument node?</p>