title: adding a calculated column for date difference in c#
body: <p>I need to add a calculated column to my DataTable that works out the number of days different between a given date and the current date. I've googled this but cannot find anything this specific.</p>
  
  <p>I've tried using the formula i have on the SQL side, but it doesn't work when building a DataTable in .net c#</p>
  
  <pre><code>OrderHeaders.Columns.Add("AGE", typeof(string), "datediff(day,[DATE_ADDED],getdate())");
  </code></pre>
  
  <p>Any ideas how I can achieve this?</p>