title: Cannot get sum on dataview field
body: <p>I try to get a list from a dataview containing a sum and grouped by some fields.</p>
  <pre><code>DataView view = _objManager.ACCOUNTS.DefaultView;
                      
                      // Set RowStateFilter to display the current rows.
                      view.RowStateFilter = DataViewRowState.CurrentRows;
  
                      var res = ((DataTable)view.Table)
                        .AsEnumerable()
                        .GroupBy(row =&gt; new { ID = row.Field&lt;long?&gt;(&quot;ID&quot;), ELEM = row.Field&lt;string&gt;(&quot;ELEM&quot;) })
                        .Select(sel =&gt; new
                        {
                            NAME = sel.First()[&quot;NAME&quot;],
                            ID = sel.First()[&quot;ID&quot;],
                            IBAN = sel.First()[&quot;IBAN&quot;],
                            BIC = sel.First()[&quot;BIC&quot;],
                            INFO = sel.First()[&quot;INFO&quot;],
                AMOUNT= sel.Sum(s =&gt; s.Sum()[&quot;AMOUNT&quot;])  //doesn't work                           
                        }).ToList();
  </code></pre>
  <p>But the sum doesn't compile.
  Do you have and idea ?
  Thanks a lot in advance.
  Eric</p>