XML : How to make a copy of a XML node with all their child nodes and values but different name C# .NET

I'm trying to make a copy of a XML node and all their child nodes but different XML parent node name, but is throwing me an error, this is the xml file:

  <Servers>    <MyServer>      <Host>0.0.0.0</Host>       <Port>12</Port>       <User>USER</User>    </MyServer>  </Servers>    

What I'm trying to do is a copy of MyServer with all their child nodes and values but different name... something like this

  <Servers>    <MyServer>      <Host>0.0.0.0</Host>       <Port>12</Port>       <User>USER</User>    </MyServer>    <MyCopyofMyServer>      <Host>0.0.0.0</Host>       <Port>12</Port>       <User>USER</User>    </MyCopyofMyServer>  </Servers>    

What I did was this:

   public void CopyInterface(string NewServer, string ServerToCopy)   {      xmldoc.Load(XMLInterfacesFile);      XmlNode NodeToCopy = xmldoc.SelectSingleNode("Servers/" + ServerToCopy);      XmlNode deep = NodeToCopy.CloneNode(true);          deep.InnerXml = deep.InnerXml.Replace(ServerToCopy, NewServer);      xmldoc.AppendChild(deep);   //Throwing an exception here!      xmldoc.Save(XMLInterfacesFile);               }    

Exception: This document already has a 'DocumentElement' node.

Any Idea?