Merge two DataColumns of type DateTime
<p>i have a datatable which contains two Datacolumns (date_start,date_sent) and i wanted to merge them into one single column (date_order) to then apply a sort like this:</p>

<pre><code>DataRow[] dtSorted = dt.Select(null, "date_order DESC",DataViewRowState.CurrentRows);
</code></pre>

<p>Since whenever date_start is null, date_sent is not and vice versa, i tried the following expression to the datacolumn:</p>

<pre><code>dt.Columns.Add("date_order", typeof(String), "IIF(date_start=NULL,date_sent,date_start)");
</code></pre>

<p>but its not working.Tried something like "ISNULL(date_start,date_sent),date_start" and "date_start + date_sent" but they didn't work either.</p>

<p>Can someone please tell me what expression i should use? Thank you.</p>
