Adding attributes to an XML node

How can I create an xml file dynamically, with the following structure?

<Login>
  <id userName="Tushar" passWord="Tushar">
      <Name>Tushar</Name>
      <Age>24</Age>
  </id>
</Login>

I am not able to create the attributes inside the id tag (i.e. userName="" and passWord="").

I am using C# in a windows application.

Some Important namespace that you might require is

using System.Xml;
using System.IO;