导出使用NPOI

调用：

 DataTable table = new DataTable();
            #region 创建 datatable
            table.Columns.Add(new DataColumn("账号", typeof(string)));
            table.Columns.Add(new DataColumn("姓名", typeof(string)));
            #endregion

            #region 填充数据
            DataRow row = null;
            foreach (var item in list)
            {
                row = table.NewRow();
                row[0] = item.Account;
                row[1] = item.Name;
                table.Rows.Add(row);
            } 
            #endregion

            return ExportExcelBase(table, "导出测试");

基类：

/// <summary>
        /// 
        /// </summary>
        /// <param name="table">datatable</param>
        /// <param name="fileName">文件名称</param>
        /// <param name="strHeaderText">表头文本</param>
        /// <returns></returns>
        [NonAction]
        protected FileContentResult ExportExcelBase(DataTable table, string fileName, string strHeaderText = null)
        {
            if (string.IsNullOrEmpty(fileName))
            {
                fileName = DateTime.Now.ToString("yyyyMMddHHmmss") + ".xls";
            }
            else
            {
                fileName = fileName + DateTime.Now.ToString("yyyyMMddHHmmss") + ".xls";
            }
            string headerName = strHeaderText ?? fileName;
            if (string.Compare(Request.Browser.Browser, "IE", true) == 0 ||
               string.Compare(Request.Browser.Browser, "InternetExplorer", true) == 0)//ie 需要编码
            {
                fileName = HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8);
            }
return File(ExportExcelFromDataTable(table, headerName).GetBuffer(),
                "application/vnd.ms-excel", fileName);
        }

以下方法从网上找来：

/// <summary>
        /// DataTable导出到Excel的MemoryStream
        /// </summary>
        /// <param name="dtSource">源DataTable</param>  
        /// <param name="strHeaderText">表头文本</param>  
        /// <returns></returns>
        public MemoryStream ExportExcelFromDataTable(DataTable dtSource, string strHeaderText = null)
        {
            var workbook = new HSSFWorkbook();
            var sheet = workbook.CreateSheet();

            #region 右击文件 属性信息
            //{  
            //    DocumentSummaryInformation dsi = PropertySetFactory.CreateDocumentSummaryInformation();  
            //    dsi.Company = "http://www.yongfa365.com/";  
            //    workbook.DocumentSummaryInformation = dsi;  

            //    SummaryInformation si = PropertySetFactory.CreateSummaryInformation();  
            //    si.Author = "柳永法"; //填加xls文件作者信息  
            //    si.ApplicationName = "NPOI测试程序"; //填加xls文件创建程序信息  
            //    si.LastAuthor = "柳永法2"; //填加xls文件最后保存者信息  
            //    si.Comments = "说明信息"; //填加xls文件作者信息  
            //    si.Title = "NPOI测试"; //填加xls文件标题信息  
            //    si.Subject = "NPOI测试Demo";//填加文件主题信息  
            //    si.CreateDateTime = DateTime.Now;  
            //    workbook.SummaryInformation = si;  
            //}
            #endregion

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

            //取得列宽  
            var arrColWidth = new int[dtSource.Columns.Count];
            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 < dtSource.Columns.Count; j++)
                {
                    int intTemp = Encoding.GetEncoding(936).GetBytes(dtSource.Rows[i][j].ToString()).Length;
                    if (intTemp > arrColWidth[j])
                    {
                        arrColWidth[j] = intTemp;
                    }
                }
            }



            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();
                    }

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

                        var headStyle = workbook.CreateCellStyle();
                        headStyle.Alignment = HorizontalAlignment.Center;
                        var font = workbook.CreateFont();
                        font.FontHeightInPoints = 20;
                        font.Boldweight = 700;
                        headStyle.SetFont(font);

                        headerRow.GetCell(0).CellStyle = headStyle;

                        sheet.AddMergedRegion(new CellRangeAddress(0, 0, 0, dtSource.Columns.Count - 1));
                        //headerRow.Dispose();  
                    }
                    #endregion


                    #region 列头及样式
                    {
                        var headerRow = sheet.CreateRow(1);


                        var headStyle = workbook.CreateCellStyle();
                        headStyle.Alignment = HorizontalAlignment.Center;
                        var font = workbook.CreateFont();
                        font.FontHeightInPoints = 10;
                        font.Boldweight = 700;
                        headStyle.SetFont(font);


                        foreach (DataColumn column in dtSource.Columns)
                        {
                            headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);
                            headerRow.GetCell(column.Ordinal).CellStyle = headStyle;

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

                        }
                        //headerRow.Dispose();  
                    }
                    #endregion

                    rowIndex = 2;
                }
                #endregion


                #region 填充内容
                var dataRow = sheet.CreateRow(rowIndex);
                foreach (DataColumn column in dtSource.Columns)
                {
                    var newCell = dataRow.CreateCell(column.Ordinal);

                    var drValue = row[column].ToString();

                    switch (column.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 (var ms = new MemoryStream())
            {
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;

                // sheet.Dispose();  
                //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;
            }
        }