Here's an alternate method to Danko's idea that would also use the MouseDown event of the grid.

private void ultraGrid1_MouseDown(object sender, MouseEventArgs e)
{
    String groupbytext = String.Empty;
    if (ultraGrid1.DisplayLayout.UIElement.ElementFromPoint(e.Location) is DependentTextUIElement &&
        ultraGrid1.Selected.Rows.Count > 0 && ultraGrid1.Selected.Rows[0].IsGroupByRow == true)
        groupbytext = ((UltraGridGroupByRow)ultraGrid1.Selected.Rows[0]).ValueAsDisplayText;
}

The code snippet here is dependent on the user clicking the GroupBy row.

Do you really want the value only when the user clicks on the row? What if they activate the row using the keyboard?

If you only care about clicking, then using MouseDown as Danko suggested is a good way to go. If you just want to track when the ActiveRow changes, I would do it like this:

        private void ultraGrid1_AfterRowActivate(object sender, EventArgs e)
        {
            UltraGrid grid = (UltraGrid)sender;
            if (grid.ActiveRow != null && grid.ActiveRow.IsGroupByRow)
            {
                UltraGridGroupByRow groupByRow = (UltraGridGroupByRow)grid.ActiveRow;
                Debug.WriteLine((groupByRow.Value);
            }
        }

Either way, you get the value by casting the row into an UltraGridGroupByRow and then using the Value property.

Hello Oliver,

One possible apporach might be using MouseDown event of the UltraGrid and get the value of the GroupByRow like the following:

  private void ultraGrid1_MouseDown(object sender, MouseEventArgs e)
        {
            GroupByRowUIElement rowUI = Get(((sender as UltraGrid).DisplayLayout.UIElement.ElementFromPoint(e.Location)));
            if( rowUI != null)
            {

               //get the desired value of the clicked GroupByRow
                rowUI.GroupByRow.Value.ToString();
            }
        }
        private GroupByRowUIElement Get(UIElement elemet)
        {
            if (elemet == null)
                return null;
            if (elemet is GroupByRowUIElement)
                return (GroupByRowUIElement)elemet;
            return Get(elemet.Parent);
        } 

Please let me know if this is not what you are looking for.