เรื่องการส่งค่า parameter ในตอนกด Next Page Crystal Report

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Microsoft.VisualBasic;
using System.Collections;
using System.Data;
using System.Diagnostics;
using CrystalDecisions.CrystalReports.Engine;
using System.Data.SqlClient;
using System.Text;
using CrystalDecisions.Shared;

namespace Helpdesk
{
    public partial class report_jobm : System.Web.UI.Page
    {
        oCenter oC = new oCenter();
        protected void Page_Load(object sender, EventArgs e)
        {
            ConfigureCrystalReports();
        }

        private ReportDocument rpt;

        void ConfigureCrystalReports()
        {
            
            rpt = new ReportDocument();
            rpt.Load(Server.MapPath("report4.rpt"));
            TableLogOnInfo crtableLogoninfo = new TableLogOnInfo();
            ConnectionInfo crConnectionInfo = new ConnectionInfo();
            Tables CrTables;

            crConnectionInfo.ServerName = "TOEY-PC";
            crConnectionInfo.DatabaseName = "Helpdesk";
            crConnectionInfo.UserID = "sa";
            crConnectionInfo.Password = "password";
            CrTables = rpt.Database.Tables;

            foreach (CrystalDecisions.CrystalReports.Engine.Table CrTable in CrTables)
            {
                crtableLogoninfo = CrTable.LogOnInfo;
                crtableLogoninfo.ConnectionInfo = crConnectionInfo;
                CrTable.ApplyLogOnInfo(crtableLogoninfo);
            }

            rpt.SetParameterValue("startdate", Session["startdate"].ToString());
            rpt.SetParameterValue("enddate", Session["enddate"].ToString());
            this.CrystalReportViewer1.ReportSource = rpt;
            CrystalReportViewer1.PrintMode = CrystalDecisions.Web.PrintMode.ActiveX;
            Session["ReportSource1"] = rpt;
        }

        protected override void OnUnload(EventArgs e)
        {
            base.OnUnload(e);

            try
            {
                if (rpt != null)
                {
                  
                    rpt.Close();
                    rpt.Dispose();
                    GC.Collect();
                }

            }
            catch (Exception ex)
            {
                // Exception
            }
        }

        protected void rptCrystal_Unload(object sender, EventArgs e)
        {
            try
            {
                if (rpt != null)
                {
                    rpt.Close();
                    rpt.Dispose();
                    GC.Collect();
                }

            }
            catch (Exception ex)
            {
                // Exception
            }
        }

    }
}