property Column.ExpandColumns as String
Specifies the list of columns to be shown when the current column is expanded.

TypeDescription
String A String expression that specifies the list of columns to be shown/hidden when the current column is expanded or collapsed. The list indicates the index of each column to be shown/hidden separated by comma character. For instance, "2,3" indicates that the columns with the index 2 and 3 are displayed bellow the current column.
By default, the ExpandColumns property is empty. Use the ExpandColumns property to display the columns on multiple levels, or to allow your users to expand/collapse the columns. The DisplayExpandButton property specifies whether the column's header displays a +/- ( expanding button ), to let user expands or collapse the column, when it is clicked. The Expanded property expands programmatically a column. The control fires the ViewEndChanging(exLayoutChange) event when the user expands or collapse a column. Use the ExpandItem property to expand or collapse an item. The Index property indicates the column's index. The Visible property specifies whether a column is Visible or hidden.

The control performs showing/hiding the child columns as follow:

The following screen shot shows the control's expandable header:

The following movie shows how you can use the Expandable Header support.