private void pivotGridControl1_CustomFieldSort(object sender, PivotGridCustomFieldSortEventArgs e)
        {
            if (!rowField.Equals(e.Field))
            {
                return;
            }
            string value1  = e.Value1.ToString();
            string value2  = e.Value2.ToString();
            int    length1 = value1.Length;
            int    length2 = value2.Length;

            e.Result = Comparer <int> .Default.Compare(length1, length2);

            if (e.Result == 0)
            {
                e.Result = Comparer <string> .Default.Compare(value1, value2);
            }
            e.Handled = true;
        }