DataTable导出到Excel文件

调用方法：
ExcelHelper.Export(dtTemp, "供应商App", DlgSave.FileName, "物料文档"
                        , new string[10] { "MatterCode", "MatterName", "MatterType", "MainUnit", "TagModelName", "LotName", "FMatterCode", "FMatterName", "FMatterType", "TagNumber" }
                        , new string[10] { "MatterCode", "MatterName", "MatterType", "MainUnit", "TagModelName", "LotName", "FMatterCode", "FMatterName", "FMatterType", "TagNumber" });

        /// <summary>   
        /// DataTable导出到Excel文件   
        /// </summary>   
        /// <param name="dtSource">源DataTable</param>   
        /// <param name="strHeaderText">表头文本</param>   
        /// <param name="strFileName">保存位置</param>
        /// <param name="strSheetName">工作表名称</param>
        public static void Export(DataTable dtSource, string strHeaderText, string strFileName, string strSheetName, string[] oldColumnNames, string[] newColumnNames)
        {
            if (strSheetName == "")
            {
                strSheetName = "Sheet";
            }
            using (MemoryStream ms = Export(dtSource, strHeaderText, strSheetName, oldColumnNames, newColumnNames))
            {
                using (FileStream fs = new FileStream(strFileName, FileMode.Create, FileAccess.Write))
                {
                    byte[] data = ms.ToArray();
                    fs.Write(data, 0, data.Length);
                    fs.Flush();
                }
            }
        }

        /// <summary>   
        /// DataTable导出到Excel的MemoryStream   
        /// </summary>   
        /// <param name="dtSource">源DataTable</param>   
        /// <param name="strHeaderText">表头文本</param>   
        /// <param name="strSheetName">工作表名称</param>
        public static MemoryStream Export(DataTable dtSource, string strHeaderText, string strSheetName, string[] oldColumnNames, string[] newColumnNames)
        {
            if (oldColumnNames.Length != newColumnNames.Length)
            {
                return new MemoryStream();
            }
            HSSFWorkbook workbook = new HSSFWorkbook();
            //HSSFSheet sheet = workbook.CreateSheet();// workbook.CreateSheet();
            ISheet sheet = workbook.CreateSheet(strSheetName);

            #region 右击文件 属性信息
            {
                DocumentSummaryInformation dsi = PropertySetFactory.CreateDocumentSummaryInformation();
                dsi.Company = "";
                workbook.DocumentSummaryInformation = dsi;

                SummaryInformation si = PropertySetFactory.CreateSummaryInformation();
                //填加xls文件作者信息   
                si.Author = "";
                si.ApplicationName = "";            //填加xls文件创建程序信息   
                si.LastAuthor = "";           //填加xls文件最后保存者信息   
                si.Comments = "";      //填加xls文件作者信息   
                si.Title = strHeaderText;               //填加xls文件标题信息   
                si.Subject = strHeaderText;              //填加文件主题信息   
                si.CreateDateTime = DateTime.Now;
                workbook.SummaryInformation = si;
            }
            #endregion

            ICellStyle dateStyle = workbook.CreateCellStyle();
            IDataFormat format = workbook.CreateDataFormat();
            dateStyle.DataFormat = format.GetFormat("yyyy-mm-dd");

            #region 取得列宽
            int[] arrColWidth = new int[oldColumnNames.Length];
            for (int i = 0; i < oldColumnNames.Length; i++)
            {
                arrColWidth[i] = Encoding.GetEncoding(936).GetBytes(newColumnNames[i]).Length;
            }
            /*
            foreach (DataColumn item in dtSource.Columns)
            {
                arrColWidth[item.Ordinal] = Encoding.GetEncoding(936).GetBytes(item.ColumnName.ToString()).Length;
            }
             * */

            for (int i = 0; i < dtSource.Rows.Count; i++)
            {
                for (int j = 0; j < oldColumnNames.Length; j++)
                {
                    int intTemp = Encoding.GetEncoding(936).GetBytes(dtSource.Rows[i][oldColumnNames[j]].ToString()).Length;
                    if (intTemp > arrColWidth[j])
                    {
                        arrColWidth[j] = intTemp;
                    }
                }
                /*
                for (int j = 0; j < dtSource.Columns.Count; j++)
                {
                    int intTemp = Encoding.GetEncoding(936).GetBytes(dtSource.Rows[i][j].ToString()).Length;
                    if (intTemp > arrColWidth[j])
                    {
                        arrColWidth[j] = intTemp;
                    }
                }
                 * */
            }
            #endregion
            int rowIndex = 0;

            foreach (DataRow row in dtSource.Rows)
            {
                #region 新建表，填充表头，填充列头，样式
                if (rowIndex == 65535 || rowIndex == 0)
                {
                    if (rowIndex != 0)
                    {
                        sheet = workbook.CreateSheet(strSheetName + ((int)rowIndex / 65535).ToString());
                    }

                    #region 表头及样式
                    //{
                    //    IRow headerRow = sheet.CreateRow(0);
                    //    headerRow.HeightInPoints = 25;
                    //    headerRow.CreateCell(0).SetCellValue(strHeaderText);

                    //    ICellStyle headStyle = workbook.CreateCellStyle();
                    //    headStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.CENTER;
                    //    IFont font = workbook.CreateFont();
                    //    font.FontHeightInPoints = 20;
                    //    font.Boldweight = 700;
                    //    headStyle.SetFont(font);

                    //    headerRow.GetCell(0).CellStyle = headStyle;
                    //    //sheet.AddMergedRegion(new Region(0, 0, 0, dtSource.Columns.Count - 1));
                    //    sheet.AddMergedRegion(new NPOI.SS.Util.CellRangeAddress(0, 0, 0, oldColumnNames.Length - 1));
                    //}
                    #endregion

                    #region 列头及样式
                    {
                        //HSSFRow headerRow = sheet.CreateRow(1);
                        IRow headerRow = sheet.CreateRow(0);

                        ICellStyle headStyle = workbook.CreateCellStyle();
                        headStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.CENTER;
                        IFont font = workbook.CreateFont();
                        font.FontHeightInPoints = 10;
                        font.Boldweight = 700;
                        headStyle.SetFont(font);

                        for (int i = 0; i < oldColumnNames.Length; i++)
                        {
                            headerRow.CreateCell(i).SetCellValue(newColumnNames[i]);
                            headerRow.GetCell(i).CellStyle = headStyle;
                            //设置列宽
                            sheet.SetColumnWidth(i, (arrColWidth[i] + 1) * 256);
                        }
                        /*
                        foreach (DataColumn column in dtSource.Columns)
                        {
                            headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);
                            headerRow.GetCell(column.Ordinal).CellStyle = headStyle;

                            //设置列宽   
                            sheet.SetColumnWidth(column.Ordinal, (arrColWidth[column.Ordinal] + 1) * 256);
                        }
                         * */
                    }
                    #endregion

                    rowIndex = 1;
                }
                #endregion

                #region 填充内容
                IRow dataRow = sheet.CreateRow(rowIndex);
                //foreach (DataColumn column in dtSource.Columns)
                for (int i = 0; i < oldColumnNames.Length; i++)
                {
                    ICell newCell = dataRow.CreateCell(i);

                    string drValue = row[oldColumnNames[i]].ToString();

                    switch (dtSource.Columns[oldColumnNames[i]].DataType.ToString())
                    {
                        case "System.String"://字符串类型   
                            newCell.SetCellValue(drValue);
                            break;
                        case "System.DateTime"://日期类型   
                            DateTime dateV;
                            DateTime.TryParse(drValue, out dateV);
                            newCell.SetCellValue(dateV);

                            newCell.CellStyle = dateStyle;//格式化显示   
                            break;
                        case "System.Boolean"://布尔型   
                            bool boolV = false;
                            bool.TryParse(drValue, out boolV);
                            newCell.SetCellValue(boolV);
                            break;
                        case "System.Int16"://整型   
                        case "System.Int32":
                        case "System.Int64":
                        case "System.Byte":
                            int intV = 0;
                            int.TryParse(drValue, out intV);
                            newCell.SetCellValue(intV);
                            break;
                        case "System.Decimal"://浮点型   
                        case "System.Double":
                            double doubV = 0;
                            double.TryParse(drValue, out doubV);
                            newCell.SetCellValue(doubV);
                            break;
                        case "System.DBNull"://空值处理   
                            newCell.SetCellValue("");
                            break;
                        default:
                            newCell.SetCellValue("");
                            break;
                    }

                }
                #endregion

                rowIndex++;
            }


            using (MemoryStream ms = new MemoryStream())
            {
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;

                //sheet.Dispose();
                sheet = null;
                workbook = null;
                //workbook.Dispose();//一般只用写这一个就OK了，他会遍历并释放所有资源，但当前版本有问题所以只释放sheet   
                return ms;
            }
        }