How do I export a query to a text file?

I have done the DataTable to Excel conversion with the following code. Hope it's very easy no need to change more just copy & pest the code replace your variable with your variable, and it will work properly.

First create a folder in your solution Document, and create an Excel file MyTemplate.xlsx. you can change those name according to your requirement. But remember for that you have to change the name in code also.

Please find the following code...

    protected void GetExcel_Click(object sender, EventArgs e)
    {            

        ManageTicketBS objManageTicket = new ManageTicketBS();
        DataTable DT = objManageTicket.GetAlldataByDate();   //this function will bring the data in DataTable format, you can use your function instate of that.  

        string DownloadFileName;
        string FolderPath;
        string FileName = "MyTemplate.xlsx";
        DownloadFileName = Path.GetFileNameWithoutExtension(FileName) + new Random().Next(10000, 99999) + Path.GetExtension(FileName);
        FolderPath = ".\\" + DownloadFileName;

        GetParents(Server.MapPath("~/Document/" + FileName), Server.MapPath("~/Document/" + DownloadFileName), DT);

        string path = Server.MapPath("~/Document/" + FolderPath);
        FileInfo file = new FileInfo(path);
        if (file.Exists)
        {
            try
            {
                HttpResponse response = HttpContext.Current.Response;
                response.Clear();
                response.ClearContent();
                response.ClearHeaders();
                response.Buffer = true;
                response.ContentType = MimeType(Path.GetExtension(FolderPath));
                response.AddHeader("Content-Disposition", "attachment;filename=" + DownloadFileName);
                byte[] data = File.ReadAllBytes(path);
                response.BinaryWrite(data);
                HttpContext.Current.ApplicationInstance.CompleteRequest();
                response.End();
            }

            catch (Exception ex)
            {
                ex.ToString();
            }
            finally
            {
                DeleteOrganisationtoSupplierTemplate(path);
            }
        }
    }
    public string GetParents(string FilePath, string TempFilePath, DataTable DTTBL)
    {
        File.Copy(Path.Combine(FilePath), Path.Combine(TempFilePath), true);
        FileInfo file = new FileInfo(TempFilePath);
        try
        {
            DatatableToExcel(DTTBL, TempFilePath, 0);

            return TempFilePath;

        }

        catch (Exception ex)
        {                
            return "";
        }

    }


    public static string MimeType(string Extension)
    {
        string mime = "application/octetstream";
        if (string.IsNullOrEmpty(Extension))
            return mime;
        string ext = Extension.ToLower();
        Microsoft.Win32.RegistryKey rk = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
        if (rk != null && rk.GetValue("Content Type") != null)
            mime = rk.GetValue("Content Type").ToString();
        return mime;
    }


    static bool DeleteOrganisationtoSupplierTemplate(string filePath)
    {
        try
        {                
            File.Delete(filePath);
            return true;
        }
        catch (IOException)
        {               
            return false;
        }
    }


    public void DatatableToExcel(DataTable dtable, string pFilePath, int excelSheetIndex=1)
    {

        try
        {
            if (dtable != null && dtable.Rows.Count > 0)
            {
                IWorkbook workbook = null;
                ISheet worksheet = null;

                using (FileStream stream = new FileStream(pFilePath, FileMode.Open, FileAccess.ReadWrite))
                {

                    workbook = WorkbookFactory.Create(stream);
                    worksheet = workbook.GetSheetAt(excelSheetIndex);

                    int iRow = 1;



                    foreach (DataRow row in dtable.Rows)
                    {
                        IRow file = worksheet.CreateRow(iRow);
                        int iCol = 0;
                        foreach (DataColumn column in dtable.Columns)
                        {
                            ICell cell = null;
                            object cellValue = row[iCol];

                            switch (column.DataType.ToString())
                            {
                                case "System.Boolean":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.Boolean);

                                        if (Convert.ToBoolean(cellValue)) { cell.SetCellFormula("TRUE()"); }
                                        else { cell.SetCellFormula("FALSE()"); }

                                        //cell.CellStyle = _boolCellStyle;
                                    }
                                    break;

                                case "System.String":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.String);
                                        cell.SetCellValue(Convert.ToString(cellValue));
                                    }
                                    break;

                                case "System.Int32":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.Numeric);
                                        cell.SetCellValue(Convert.ToInt32(cellValue));
                                        //cell.CellStyle = _intCellStyle;
                                    }
                                    break;
                                case "System.Int64":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.Numeric);
                                        cell.SetCellValue(Convert.ToInt64(cellValue));
                                        //cell.CellStyle = _intCellStyle;
                                    }
                                    break;
                                case "System.Decimal":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.Numeric);
                                        cell.SetCellValue(Convert.ToDouble(cellValue));
                                        //cell.CellStyle = _doubleCellStyle;
                                    }
                                    break;
                                case "System.Double":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.Numeric);
                                        cell.SetCellValue(Convert.ToDouble(cellValue));
                                        //cell.CellStyle = _doubleCellStyle;
                                    }
                                    break;

                                case "System.DateTime":
                                    if (cellValue != DBNull.Value)
                                    {
                                        cell = file.CreateCell(iCol, CellType.String);
                                        DateTime dateTime = Convert.ToDateTime(cellValue);
                                        cell.SetCellValue(dateTime.ToString("dd/MM/yyyy"));

                                        DateTime cDate = Convert.ToDateTime(cellValue);
                                        if (cDate != null && cDate.Hour > 0)
                                        {
                                            //cell.CellStyle = _dateTimeCellStyle; 
                                        }
                                        else
                                        {
                                            // cell.CellStyle = _dateCellStyle; 
                                        }
                                    }
                                    break;
                                default:
                                    break;
                            }
                            iCol++;
                        }
                        iRow++;
                    }
                    using (var WritetoExcelfile = new FileStream(pFilePath, FileMode.Create, FileAccess.ReadWrite))
                    {
                        workbook.Write(WritetoExcelfile);
                        WritetoExcelfile.Close();
                        //workbook.Write(stream);
                        stream.Close();
                    }
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

This code you just need to copy & pest in your script and add the Namespace as following, Also change the excel file name as previously discussed.