使用NPOI库导入导出EXCEL

 /// <summary>
        /// NPOI 导入excel
        /// </summary>
        /// <returns></returns>
        [HttpPost]
        public ActionResult NPOIInport()
        {
            bool isok = false;
            string msg = string.Empty;
            var file = Request.Files["Importexcelfile"];//接收的文件对象
            var filename = SaveUploadExcel(file);//将文件保存至某一路径下 并形成新的文件名称
            var filePath=System.Configuration.ConfigurationManager.AppSettings["Upload"] + @"\excel\" + filename;//新路径
            IWorkbook workbook = null; //定义工作簿接口
            ISheet sheet=null;//定义sheet表
            DataTable data = new DataTable();
            FileStream filestream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
            if (file.ContentLength>0)
            {
                if (filePath.IndexOf(".xlsx") > 0)
                {
                    workbook = new XSSFWorkbook(filestream);//.xlsx 文件
                }
                else
                {
                    workbook = new HSSFWorkbook(filestream);//.xls文件
                }
                sheet = workbook.GetSheetAt(0);//默认第一个sheet sheet 下标
                //sheet = workbook.GetSheet("sheet的名字");//获取想要查询sheet的名字
                if (sheet!=null)
                {
                    for (int i = 0; i < sheet.LastRowNum; i++)
                    {
                        IRow row = sheet.GetRow(i);//获取第一行 一般都是表头
                        var firstvalue = row.GetCell(0);//第一行的第一列
                        var secondvalue = row.GetCell(1);
                    }
                    //常见读取excel 已经够用  实际项目中会遇到 再次封装数据形成table  一般这个帮助类会叫**Helper
                    IRow firstrow = sheet.GetRow(0);
                    int cellcount = firstrow.LastCellNum;//总列数
                    for (int i = firstrow.FirstCellNum; i < cellcount; i++)
                    {
                        ICell icell = firstrow.GetCell(i);
                        if (icell!=null)
                        {
                            string cellvalue = icell.StringCellValue;//获取当前单元格的value
                            DataColumn column = new DataColumn(cellvalue);
                            data.Columns.Add(column);//添加表头
                        }
                    }
                    int startrow = sheet.FirstRowNum + 1;
                    for (int i = startrow; i < sheet.LastRowNum; i++)
                    {
                        IRow row = sheet.GetRow(i);
                        if (row!=null)
                        {
                            DataRow datarow = data.NewRow();
                            for (int j = row.FirstCellNum; j < cellcount; j++)
                            {
                                if (row.GetCell(j)!=null)
                                {
                                    datarow[j] = row.GetCell(j).ToString();
                                }
                            }
                            data.Rows.Add(datarow);
                        }
                    }
                    //return data;
                }
                
            }
            return Json(new { Isok = isok, Msg = msg });
        }
        public static string SaveUploadExcel(HttpPostedFileBase fileexcel)
        {
            string filename = fileexcel.FileName;
            string extension = Path.GetExtension(filename);
            int filesize = fileexcel.ContentLength;
            if (filesize>int.Parse(System.Configuration.ConfigurationManager.AppSettings["UploadFileSize"]))
            {
                return "文件超过上限";
            }
            string dirPath = System.Configuration.ConfigurationManager.AppSettings["Upload"] + @"\excel\";
            //生成新的文件名
            string newFileName = string.Format("{0}{1}", DateTime.Now.ToString("yyMMddHHmmssfffffff"), extension);

            if (!Directory.Exists(dirPath))
                Directory.CreateDirectory(dirPath);
            fileexcel.SaveAs(dirPath + newFileName);
            //返回新生成的文件名称
            return newFileName;
        }