title: SUM datatable column with compute but NO filter
body: <p>this seems to work when i put an item in it to filter, but i don't want to add a filter, ie just happy to sum the column and that's it.</p>
  
  <p>i've tried passing in string.empty and "" but no joy:</p>
  
  <pre><code>object objColTotal;
  objColTotal = _dataSetDataTable.Compute("Sum(Price)", "");
  decimal tot = Convert.ToDecimal(objColTotal);
  </code></pre>