title: sum string datatype of a datatable
body: <p>I want to compute the sum of a string datatype column in a datatable.</p>
  
  <p>I have already tried this:</p>
  
  <pre><code>Int32 omarks = Convert.ToInt32(dt.Compute("Sum(Convert(Marks, 'System.Int32'))", ""));
  tbobtained.Text = omarks.ToString();
  </code></pre>
  
  <p>But i'm getting this error:</p>
  
  <p>Syntax Error in Aggregate argument: Expecting a single column argument with a possible child qualifier.</p>