protected void FillGrid()
    {
        DateTime fromDate = DateTime.MinValue; // IsValidDate(txtStartDate.Text) ? GetDate(txtStartDate.Text) : DateTime.MinValue;
        DateTime toDate   = IsValidDate(txtEndDate.Text)   ? GetDate(txtEndDate.Text)   : DateTime.MinValue;
        DateTime nNoRecallLettersAfterDate = IsValidDate(txtNoRecallLettersAfterDate.Text) ? GetDate(txtNoRecallLettersAfterDate.Text) : DateTime.MinValue;


        //DataTable dt = PatientDB.GetRecallPatients(fromDate, toDate, chkOnlyShowIfHasEPCs.Checked, Convert.ToInt32(ddlClinics.SelectedValue));
        DataTable dt = PatientDB.GetRecallPatients(fromDate, toDate, false, Convert.ToInt32(ddlClinics.SelectedValue));



        int[] patientIDs = new int[dt.Rows.Count];
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            patientIDs[i] = Convert.ToInt32(dt.Rows[i]["patient_patient_id"]);
        }


        Hashtable mostRecentRecallHashByPatientID = LetterPrintHistoryDB.GetMostRecentRecallHashByPatients(patientIDs);


        Hashtable patientHealthCardCache        = PatientsHealthCardsCacheDB.GetBullkActive(patientIDs);
        Hashtable epcRemainingCache             = GetEPCRemainingCache(patientHealthCardCache);
        Hashtable patientsMedicareCountCache    = PatientsMedicareCardCountThisYearCacheDB.GetBullk(patientIDs, DateTime.Today.Year);
        Hashtable patientsEPCRemainingCache     = PatientsEPCRemainingCacheDB.GetBullk(patientIDs, DateTime.Today.AddYears(-1));
        int       MedicareMaxNbrServicesPerYear = Convert.ToInt32(SystemVariableDB.GetByDescr("MedicareMaxNbrServicesPerYear").Value);


        ArrayList remainingPatientIDs = new ArrayList();

        dt.Columns.Add("epc_expire_date", typeof(DateTime));
        dt.Columns.Add("has_valid_epc", typeof(Boolean));
        dt.Columns.Add("epc_count_remaining", typeof(Int32));

        dt.Columns.Add("most_recent_recall_sent", typeof(DateTime));
        for (int i = dt.Rows.Count - 1; i >= 0; i--)
        {
            int patientID = Convert.ToInt32(dt.Rows[i]["patient_patient_id"]);

            HealthCard hc     = GetHealthCardFromCache(patientHealthCardCache, patientID);
            bool       hasEPC = hc != null && hc.DateReferralSigned != DateTime.MinValue;
            HealthCardEPCRemaining[] epcsRemaining = !hasEPC ? new HealthCardEPCRemaining[] { } : GetEPCRemainingFromCache(epcRemainingCache, hc);
            int totalServicesAllowedLeft           = !hasEPC ? 0 : (MedicareMaxNbrServicesPerYear - (int)patientsMedicareCountCache[patientID]);

            int totalEpcsRemaining = 0;
            for (int j = 0; j < epcsRemaining.Length; j++)
            {
                totalEpcsRemaining += epcsRemaining[j].NumServicesRemaining;
            }

            DateTime referralSignedDate = !hasEPC ? DateTime.MinValue : hc.DateReferralSigned.Date;
            DateTime hcExpiredDate      = !hasEPC ? DateTime.MinValue : referralSignedDate.AddYears(1);
            bool     isExpired          = !hasEPC ? true              : hcExpiredDate <= DateTime.Today;

            int nServicesLeft = 0;
            if (hc != null && DateTime.Today >= referralSignedDate.Date && DateTime.Today < hcExpiredDate.Date)
            {
                nServicesLeft = totalEpcsRemaining;
            }
            if (hc != null && totalServicesAllowedLeft < nServicesLeft)
            {
                nServicesLeft = totalServicesAllowedLeft;
            }

            bool has_valid_epc       = hasEPC && !isExpired && (hc.Organisation.OrganisationID == -2 || (hc.Organisation.OrganisationID == -1 && nServicesLeft > 0));
            int  epc_count_remaining = hasEPC && hc.Organisation.OrganisationID == -1 ? nServicesLeft : -1;

            dt.Rows[i]["has_valid_epc"]       = has_valid_epc;
            dt.Rows[i]["epc_expire_date"]     = hasEPC ? hcExpiredDate : (object)DBNull.Value;
            dt.Rows[i]["epc_count_remaining"] = epc_count_remaining != -1 ? epc_count_remaining : (object)DBNull.Value;

            dt.Rows[i]["most_recent_recall_sent"] = mostRecentRecallHashByPatientID[patientID] == null ? (object)DBNull.Value : ((LetterPrintHistory)mostRecentRecallHashByPatientID[patientID]).Date;

            // remove if no valid epc and set to show only those with a valid EPC
            if (!chkShowWithEPC.Checked && has_valid_epc)
            {
                dt.Rows.RemoveAt(i);
            }
            else if (!chkShowWithNoEPC.Checked && !has_valid_epc)
            {
                dt.Rows.RemoveAt(i);
            }
            else if (nNoRecallLettersAfterDate != DateTime.MinValue && mostRecentRecallHashByPatientID[patientID] != null && ((LetterPrintHistory)mostRecentRecallHashByPatientID[patientID]).Date.Date > nNoRecallLettersAfterDate)
            {
                dt.Rows.RemoveAt(i);
            }
            else
            {
                remainingPatientIDs.Add(patientID);
            }
        }

        hiddenPatientIDs.Value = string.Join(",", (int[])remainingPatientIDs.ToArray(typeof(int)));

        Session["recallpatientinfo_data"] = dt;


        if (dt.Rows.Count > 0)
        {
            if (IsPostBack && Session["recallpatientinfo_sortexpression"] != null && Session["recallpatientinfo_sortexpression"].ToString().Length > 0)
            {
                DataView dataView = new DataView(dt);
                dataView.Sort         = Session["recallpatientinfo_sortexpression"].ToString();
                GrdPatient.DataSource = dataView;
            }
            else
            {
                GrdPatient.DataSource = dt;
            }


            try
            {
                GrdPatient.DataBind();
                GrdPatient.PagerSettings.FirstPageText = "1";
                GrdPatient.PagerSettings.LastPageText  = GrdPatient.PageCount.ToString();
                GrdPatient.DataBind();
            }
            catch (Exception ex)
            {
                SetErrorMessage("", ex.ToString());
            }
        }
        else
        {
            dt.Rows.Add(dt.NewRow());
            GrdPatient.DataSource = dt;
            GrdPatient.DataBind();

            int TotalColumns = GrdPatient.Rows[0].Cells.Count;
            GrdPatient.Rows[0].Cells.Clear();
            GrdPatient.Rows[0].Cells.Add(new TableCell());
            GrdPatient.Rows[0].Cells[0].ColumnSpan = TotalColumns;
            GrdPatient.Rows[0].Cells[0].Text       = "No Record Found";
        }
    }