title: Nesting results in DataSet by field values
body: <p>I'm using <code>DataRelation</code> <a href="http://msdn.microsoft.com/en-us/library/7sfkwf9s%28v=VS.90%29.aspx" rel="nofollow noreferrer">to nest tables</a> in a <code>DataSet</code>, to get a XML result like this:</p>
  
  <pre><code>&lt;Customer&gt;
      &lt;Name&gt;John&lt;/Name&gt;
      &lt;Age&gt;30&lt;/Age&gt;
      &lt;Sex&gt;Male&lt;/Sex&gt;
      &lt;Order&gt;
          &lt;Id&gt;123&lt;/Id&gt;
          &lt;Price&gt;200.00&lt;/Price&gt;
      &lt;/Order&gt;
  &lt;/Customer&gt;
  </code></pre>
  
  <p>I want to group the data by a field value, like sex, to get a result like this:</p>
  
  <pre><code>&lt;Male&gt;
      &lt;Customer&gt;
          &lt;Name&gt;John&lt;/Name&gt;
          &lt;Age&gt;30&lt;/Age&gt;
          &lt;Order&gt;
              &lt;Id&gt;123&lt;/Id&gt;
              &lt;Price&gt;200.00&lt;/Price&gt;
          &lt;/Order&gt;
      &lt;/Customer&gt;
  &lt;/Male&gt;
  </code></pre>
  
  <p>How can I achieve this (except by iterating the tables myself and creating new ones)?</p>
  
  <p>Thanks.</p>