title: Linq Distinct not bringing back the correct results
body: <p>I'm trying to select a distinct values from a <code>DataTable</code> using <code>Linq</code>. The <code>DataTable</code> gets populated from an excel sheet which has dynamic column apart from each excel sheet has a column name <code>SERIAL NUMBER</code> which is mandatory.</p>
  
  <p>I have a <code>DataTable</code> for demo purpose which consist of 4 serial number as:</p>
  
  <ul>
  <li>12345</li>
  <li>12345</li>
  <li>98765</li>
  <li>98765</li>
  </ul>
  
  <p>When I do </p>
  
  <pre><code>var distinctList = dt.AsEnumerable().Select(a =&gt; a).Distinct().ToList();
  </code></pre>
  
  <p>If I do </p>
  
  <pre><code>var distinctList = dt.AsEnumerable().Select(a =&gt; a.Field&lt;string&gt;("SERIAL NUMBER").Distinct().ToList();
  </code></pre>
  
  <p>Then I get the correct results, however but it only contains the one column from <code>dt</code> and not all the other columns</p>
  
  <p>I get all four records instead of 2. Can someone tell me where I'm going wrong please. </p>