This event will be raised after selection of worksheet has been changed. For example:

void InitWorksheet() 
{
  var sheet = gridControl.CurrentWorksheet;
  sheet.SelectionRangeChanged += sheet_SelectionRangeChanged;
}

void sheet_SelectionRangeChanged(object sender, RangeEventArgs args)
{
  MessageBox.Show("Selection changed: " + args.Range.ToAddress());
}

Remarks

This event will not be raised during dragging mouse on worksheet to change the selection range, this event raised only when mouse button released. To get selection range changes when mouse dragging, use the SelectionRangeChanging event.