It would be useful for the header cell for Sort-able columns to display an indication that the column can be sorted. This is useful to users when not all columns are sort-able, so they know which header cells will trigger resorting. Elsewhere in our application, we use a double headed arrow icon to indicate use can click on header to resort on the column; the app displays the up or down arrow indicating when sort order is active. Suggest adding a third Sort-Image-URL attribute to specify an image to use when column is not sorted ascending or descending. At present, best I can do declaratively (w/o custom coding) is the set one of the HeaderStyle-Font properties (for example the HeaderStyle-Font-Underline) to provide a visual indication that column is sort-able.