An AllowGroupByEnum expression that specifies where the column can be dropped on
the control's pivot bar.
By default, the AllowGroupBy property is exGroupByAny,
which indicates that the column can be dropped anywhere on the control's pivot
bar. The PivotBarVisible property
shows or hides the control's pivot bar. Use
the AllowGroupBy property to prevent the column to group by that column. For
instance, you can prevent grouping by numeric columns. Use the AllowDrop
property on False, to prevent loading the data-files ( TXT, XML files ), by
drag and drop, into the control. The AllowGroupBy property has effect for
columns dragged from the control's Columns Floating Panel ( PivotColumnsFloatBarVisible
property ), or from the control's columns header.