// Stefan: start
        protected override void OnMouseDoubleClick(MouseButtonEventArgs e)
        {
            base.OnMouseDoubleClick(e);
            var dateTimePicker = this.ParentOfType<RadDateTimePicker>();
            if (dateTimePicker != null && dateTimePicker.InputBox != null)
            {
                dateTimePicker.IsDropDownOpen = false; // close it.
            }
        }
        // Stefan: end