使用 NPOI 将数据导出至 Excel 中（可以创建多个工作表）

类：

    public class Excel
    {
        private FileStream fs = null;
        private XSSFWorkbook workbook = null;

        public Excel(string path, string fileName)
        {
            if(!path.EndsWith(@"\"))
            {
                path = path + "\\";
            }

            //如果文件夹不存在，则创建该文件夹
            if(!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }

            if(!fileName.EndsWith(".xlsx") && !fileName.EndsWith(".xls"))
            {
                fileName = fileName + ".xlsx";
            }

            fs = new FileStream(path + fileName, FileMode.OpenOrCreate);
            workbook = new XSSFWorkbook();
        }

        /// <summary>
        /// 添加工作表
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sheetName">工作表的名称</param>
        /// <param name="titleName">表题名称</param>
        /// <param name="columnNames">表头名称</param>
        /// <param name="list"></param>
        public void AddSheet<T>(string sheetName, string titleName, string[] columnNames, IList<T> list)
        {
            XSSFSheet sheet = (XSSFSheet)workbook.CreateSheet(sheetName);

            int rowIndex = 0;
            //如果有表题名称则创建表题
            if (!string.IsNullOrEmpty(titleName))
            {
                XSSFRow headRow = (XSSFRow)sheet.CreateRow(rowIndex);
                headRow.Height = 20 * 30;                               //设置表头高

                //合并单元格（ CellRangeAddress（）该方法的参数次序是：开始行号，结束行号，开始列号，结束列号。 ）
                sheet.AddMergedRegion(new NPOI.SS.Util.CellRangeAddress(0, 0, 0, columnNames.Length - 1));
                headRow.CreateCell(0, NPOI.SS.UserModel.CellType.String).SetCellValue(titleName);
                
                XSSFCellStyle headStyle = (XSSFCellStyle)workbook.CreateCellStyle();            //设置样式
                XSSFFont font = (XSSFFont)workbook.CreateFont();                                //字体
                font.FontHeightInPoints = 20;
                font.Boldweight = 700;
                headStyle.SetFont(font);
                headRow.GetCell(0).CellStyle = headStyle;

                headStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;             //水平对齐
                headStyle.VerticalAlignment = VerticalAlignment.Center;                         //垂直对齐

                rowIndex++;
            }

            //如果有表头则创建表头
            if (columnNames != null)
            {
                XSSFRow topRow = (XSSFRow)sheet.CreateRow(rowIndex);
                XSSFCellStyle topStyle = (XSSFCellStyle)workbook.CreateCellStyle();
                XSSFFont topfont = (XSSFFont)workbook.CreateFont();
                topfont.FontHeightInPoints = 10;
                topfont.Boldweight = 700;
                topStyle.SetFont(topfont);
                int tag = 0;
                foreach (string column in columnNames)
                {
                    topRow.CreateCell(tag).SetCellValue(column);
                    topRow.GetCell(tag).CellStyle = topStyle;

                    //设置列宽
                    sheet.SetColumnWidth(tag, (column.Length * 256 * 4));
                    tag++;
                }

                rowIndex++;
            }

            CreateContent(sheet, list, rowIndex);
            //workbook.Add(sheet);
        }

        /// <summary>
        /// 输出文件
        /// </summary>
        public void Output()
        {
            workbook.Write(fs);
        }

        /// <summary>
        /// 添加表内容
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sheet"></param>
        /// <param name="list"></param>
        /// <param name="nowRow"></param>
        private void CreateContent<T>(XSSFSheet sheet, IList<T> list, int nowRow)
        {
            T t = (T)Activator.CreateInstance(typeof(T));
            PropertyInfo[] propertity = t.GetType().GetProperties();//取得Model类的所有公有属性

            //4 填充内容
            int rowCount = list.Count;
            for (int i = 0; i < rowCount; i++)//循环每一条内容
            {
                int rowIndex = i + nowRow;
                XSSFRow dataRow = (XSSFRow)sheet.CreateRow(rowIndex);//创建一行

                int cellCount = propertity.Length;
                for (int j = 0; j < cellCount; j++)//循环列
                {

                    PropertyInfo pro = propertity[j];//获取第j个属性
                    object objcellvalue = pro.GetValue(list[i], null);//获取第j个属性的值
                    if (objcellvalue == DBNull.Value || objcellvalue == null)
                    {
                        objcellvalue = DBNull.Value;
                    }
                    XSSFCell newCell = (XSSFCell)dataRow.CreateCell(j);//创建一个单元格

                    string cellValue = objcellvalue == DBNull.Value || objcellvalue == null ? "" : objcellvalue.ToString();

                    #region 转换
                    switch (objcellvalue.GetType().ToString())
                    {
                        case "System.DateTime"://日期类型
                            newCell.CellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("m/d/yy h:mm");//格式化显示
                            DateTime dateV;
                            if (!DateTime.TryParse(cellValue, out dateV))
                            {
                                newCell.SetCellValue("");
                            }
                            else
                            {

                                newCell.SetCellValue(dateV);
                            }

                            break;
                        case "System.Boolean"://布尔型
                            newCell.SetCellValue(cellValue == "" ? "False" : cellValue);
                            break;
                        default:
                            newCell.SetCellValue(cellValue);
                            break;

                    }
                    #endregion
                }
            }

        }
    }

调用：

            var head = new string[] { "账号", "账号名称", "锁定客户数量", "账号状态", "最后登录时间" };
            Excel excel = new Excel("D:\\download", "测试");
            excel.AddSheet("表1", "表1表题", head, result);

            var head_data = new string[] { "URMID", "企业名称", "服务到期时间", "合作金额", "最后登录时间", "在期职位数" };
            excel.AddSheet("表2", $"{d.smanName}锁定的客户", head_data, d.cusls);
            excel.Output();