property Column.AllowGroupBy as Boolean
Specifies if the column can be grouped by.

   Boolean A Boolean expression that specifies whether the user can drag and drop the column to be grouped by,  
By default, the AllowGroupBy property is True. The AllowGroupBy property has effect only if the control's AllowGroupBy property is True. Use the AllowGroupBy property on False, to prevent a specific column to be sorted/grouped by. The same you can achieve if the AllowSort property is False. The SortBarVisible property specifies whether the control's sort bar is visible or hidden. If the control's sort bar is visible, the user can drag and drop columns to it, so the column get sorted and items grouped. The Group/Ungroup method groups or ungroup the control's list. For instance, you can remove the grouping items, by calling the Ungroup method. The GroupByFormatCell property determines the format of the cell to be displayed in the grouping item, when the column gets sorted.