Create Text File using C#

private void btnCBSUpload_Click(object sender, EventArgs e) {
    string M_FLNM, m_Str;
    StreamWriter STRWRT;
    // SqlDataReader drUpload;
    if (txtCBSAccNo.Text.Trim().Length == 0) {
        MessageBox.Show("Please Enter CMS A/c No");
        txtCBSAccNo.Focus();
        return;
    }
    if (txtCBSupload.Text.Trim().Length == 0) {
        MessageBox.Show("Please Enter File Description");
        txtCBSupload.Focus();
        return;
    }
    //if (txtLOC_code.Text.Trim() == "")
    //{
    // MessageBox.Show("Please Enter Location");
    // txtCBSupload.Focus();
    // return;
    //}
    //if (txtDepoSiteSlip.Text.Trim() == "")
    //{
    // MessageBox.Show("Please Enter Deposite Slip no.");
    // txtCBSupload.Focus();
    // return;
    //}
    FLNM = @"" + lworkPath + DateTime.Today.ToString("ddMMyyyy");
    if (!Directory.Exists(FLNM)) {
        Directory.CreateDirectory(FLNM);
    } else {
        Directory.CreateDirectory(FLNM);
    }
    // M_FLNM = @"C:\ADROIT\CTS\CBS_" + txtCBSupload.Text.Trim().ToUpper().Substring(0, Math.Min(4, txtCBSupload.Text.Length)) + "_" + DateTime.Today.ToString("ddMMyyyy") + ".txt";
    //M_FLNM = lworkPath + DateTime.Today.ToString("ddMMyyyy") + "\\" + "CBS_" + txtCBSupload.Text.Trim().ToUpper().Substring(0, Math.Min(4, txtCBSupload.Text.Length)) + "_" + DateTime.Today.ToString("ddMMyyyy") + ".txt";
    M_FLNM = lworkPath + DateTime.Today.ToString("ddMMyyyy") + "\\" + "CBS_" + txtCBSupload.Text.Trim().ToUpper().Substring(0, Math.Min(4, txtCBSupload.Text.Length)) + "_" + DateTime.Today.ToString("ddMMyyyy") + ".txt";
    if (!File.Exists(M_FLNM)) {
        STRWRT = new StreamWriter(M_FLNM);
    } else {
        GC.Collect();
        GC.WaitForPendingFinalizers();
        File.Delete(M_FLNM);
        STRWRT = new StreamWriter(M_FLNM);
    }
    m_Str = (" SELECT LEFT(ENDNO,5) AS MACHINEID,ENDNO AS SEQNO,CHEQUENUMBER AS CHQNO,BRANCHCODE AS SORTCODE,TRANSACTION_CODE AS TRCD, AMOUNT AS CHQAMT, " +
        " PRESENTATIONDATE AS BANKING_DATE FROM OUTWARDBATCHSCANDETAILS WHERE CONVERT(VARCHAR,PRESENTATIONDATE,103)='" + maskCleringDate.Text + "' AND " +
        " (IsChequeStatus <> 'R' or IsChequeStatus is null) AND BATCHHID IN (SELECT DISTINCT BATCHID FROM OUTWARDBATCH WHERE CONVERT(VARCHAR,PRESENTATIONDATE,103)='" + maskCleringDate.Text + "' AND " +
        " BATCHNO BETWEEN " + txtBatchFrm.Text + " AND " + txtbatchToo.Text + " AND BATCHSTATUSID=8) ORDER BY UPLOAD_ID ");
    string maskCleringdt = Convert.ToDateTime(maskCleringDate.Text).ToString("yyyyMMdd");
    //drUpload = pr_ExeDataReader(m_Str);
    DataTable dt = clscom.GetTable4Command(m_Str);
    if (dt.Rows.Count == 0) {
        MessageBox.Show("No Data Found..");
        return;
    }
    if (dt != null) {
        //for (int i = 0; i < dt.Rows.Count; i++)
        foreach(DataRow item in dt.Rows) {
            STRWRT.WriteLine(string.Format("{0,-16}{1,-3}{2,17}{3,-1}{4,-30}{5,16}{6,17}{7,-3}{8,-9}{9,-6}{10,-6}{11,-1}{12,-1}{13,-16}{14,-8}{15,-30}{16,-5}{17,-16}{18,-34}{19,-34}{20,-40}{21,-50}{22,-50}{23,-50}{24,-50}{25,-90}",
                txtCBSAccNo.Text, "INR", Convert.ToDecimal(item["CHQAMT"]).ToString("0.00").Trim().PadLeft(17, '0').Substring(0, 17), "", item["CHQNO"], item["CHQNO"], Convert.ToDecimal(item["CHQAMT"]).ToString("0.00").Trim().PadLeft(17, '0').Substring(0, 17), item["TRCD"].ToString().PadRight(3, ' '), item["SORTCODE"], " ", " ", "N", "Y", " ", maskCleringdt, " ", " ", " ", " ", " ", " ", txtCBSupload.Text, " ", " ", " ", " "));
        }
    } else {
        MessageBox.Show("No Data Found..");
        return;
    }
    STRWRT.Close();
}
}