Change Sort Order in Group Section Dynamically

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using CrystalDecisions.CrystalReports.Engine;

namespace CrystalReportsApp
{
   public partial class frmGroupBy : Form    {
       DataTable dtCustomers = new DataTable();
       rptGroupBy rpt = new rptGroupBy();

       public frmGroupBy()
       {
           InitializeComponent();
       }

       private void SetReportDataSource()
       {
           using (SqlConnection sqlConn = new SqlConnection(
           @"Database=Northwind2005;Uid=sa;Pwd=sql2005;Server=.\SQL2005"))
           {
               using (SqlCommand sqlCmd = new SqlCommand())
               {
                   sqlCmd.CommandType = CommandType.Text;
                   sqlCmd.Connection = sqlConn;
                   sqlCmd.CommandText =
                   "Select * From Customers" +
                   " Where Region Is Not Null And Country Is Not Null";

                   if (sqlConn.State == ConnectionState.Closed) sqlConn.Open();
                   dtCustomers.Load(sqlCmd.ExecuteReader());

                   rpt.SetDataSource(dtCustomers);
                   crystalReportViewer1.ReportSource = rpt;
               }
           }
       }

       private void SortReport(bool ASC)
       {
          SortFields allSortField;
          allSortField = rpt.DataDefinition.SortFields;
          foreach (SortField aSortField in allSortField)
          {
              if (ASC)
              {
                  if (aSortField.SortType ==
                     CrystalDecisions.Shared.SortFieldType.GroupSortField)
                  {
                      if (aSortField.Field.Name == "Region")
                      {
                          aSortField.SortDirection =
                          CrystalDecisions.Shared.SortDirection.AscendingOrder;
                      }
                  }
              }
              else               {
                  if (aSortField.SortType ==
                     CrystalDecisions.Shared.SortFieldType.GroupSortField)
                  {
                      if (aSortField.Field.Name == "Region")
                      {
                          aSortField.SortDirection =
                          CrystalDecisions.Shared.SortDirection.DescendingOrder;
                      }
                  }
              }
          }
          crystalReportViewer1.ReportSource = rpt;
          crystalReportViewer1.Refresh();
       }

       private void frmGroupBy_Load(object sender, EventArgs e)
       {
           SetReportDataSource();
       }

       private void btnSortASC_Click(object sender, EventArgs e)
       {
           SortReport(true);
       }

       private void btnSortDesc_Click(object sender, EventArgs e)
       {
           SortReport(false);
       }
   }
}