C# 使用 NPOI 库读写 Excel 文件

public class ExcelHelper
    {

        /// <summary>
        /// Datable导出成Excel
        /// </summary>
        /// <param name="dt">导出存放文件夹路径</param>
        /// <param name="Route">文件夹路径</param>
        /// <param name="file">导出路径(包括文件名与扩展名),注：年月日时分秒+文件名</param>

        public static void TableToExcel(DataTable dt, string Route, string file)
        {
            string[] fileArr = file.Split(new char[] { '.' });
            file = fileArr[0] + DateTime.Now.ToString("yyyyMMddHHmmss") + "." + fileArr[1];

            IWorkbook workbook;
            string fileExt = Path.GetExtension(file).ToLower();
            if (fileExt == ".xlsx") { workbook = new XSSFWorkbook(); } else if (fileExt == ".xls") { workbook = new HSSFWorkbook(); } else { workbook = null; }
            if (workbook == null) { return; }
            ISheet sheet = string.IsNullOrEmpty(dt.TableName) ? workbook.CreateSheet("Sheet1") : workbook.CreateSheet(dt.TableName);

            //设置列宽
            //sheet.SetColumnWidth(0, 15 * 256);
            //sheet.SetColumnWidth(1, 15 * 256);
            //sheet.SetColumnWidth(2, 15 * 256);
            //sheet.SetColumnWidth(3, 15 * 256);
            //sheet.SetColumnWidth(4, 15 * 256);
            //sheet.SetColumnWidth(5, 25 * 256);
            //sheet.SetColumnWidth(6, 25 * 256);
            //sheet.SetColumnWidth(7, 30 * 256);
            //sheet.SetColumnWidth(8, 15 * 256);
            //sheet.SetColumnWidth(9, 15 * 256);
            //sheet.SetColumnWidth(10, 15 * 256);
            //sheet.SetColumnWidth(12, 15 * 256);

            //for (int i = 0; i < dt.Rows.Count; i++)
            //{
            //    sheet.SetColumnWidth(i, 20 * 256);
            //}


            //表头  
            IRow row = sheet.CreateRow(0);
            for (int i = 0; i < dt.Columns.Count - 1; i++)
            {
                ICell cell = row.CreateCell(i);
                cell.SetCellValue(dt.Columns[i].ColumnName);
            }

            //数据  
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                IRow row1 = sheet.CreateRow(i + 1);
                for (int j = 0; j < dt.Columns.Count - 1; j++)
                {
                    ICell cell = row1.CreateCell(j);

                    cell.SetCellValue(dt.Rows[i][j].ToString());
                }
            }



            //转为字节数组  
            MemoryStream stream = new MemoryStream();
            workbook.Write(stream);
            var buf = stream.ToArray();

            //如找不到文件夹则创建   
            if (!Directory.Exists(Route))
            {
                Directory.CreateDirectory(Route);
            }


            //保存为Excel文件  
            using (FileStream fs = new FileStream(Route + file, FileMode.Create, FileAccess.Write))
            {
                fs.Write(buf, 0, buf.Length);
                fs.Flush();
            }


            HttpResponse response = HttpContext.Current.Response;
            response.Clear();
            response.ClearHeaders();
            response.ClearContent();
            response.Buffer = true;
            response.AddHeader("content-disposition", string.Format("attachment; FileName={0}", file));
            response.Charset = "GB2312";
            response.ContentEncoding = Encoding.GetEncoding("GB2312");
            response.ContentType = MimeMapping.GetMimeMapping(file);
            response.WriteFile(Route + file);
            response.Flush();
            response.Close();

            //HttpResponseBase response = httpContext.Response;
            //response.Clear();
            //response.Buffer = false;
            //response.AddHeader("Accept-Ranges", "bytes");
            //response.AddHeader("Content-Type", GetContentTypeByFileName(fileName));
            //response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(Encoding.UTF8.GetBytes(fileName)));
            //response.AddHeader("Content-Length", buffer.Length.ToString());
            //response.OutputStream.Write(buffer, 0, buffer.Length);
            //response.Flush();
            //response.End();
        }



        /// <summary>
        /// Excel导入成Datable
        /// </summary>
        /// <param name="file">导入路径(包含文件名与扩展名)</param>
        /// <returns></returns>
        public static DataTable ExcelToTable(string file)
        {

            DataTable dt = new DataTable();
            IWorkbook workbook;
            string fileExt = Path.GetExtension(file).ToLower();
            using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
            {
                //XSSFWorkbook 适用XLSX格式，HSSFWorkbook 适用XLS格式
                if (fileExt == ".xlsx") { workbook = new XSSFWorkbook(fs); } else if (fileExt == ".xls") { workbook = new HSSFWorkbook(fs); } else { workbook = null; }
                if (workbook == null) { return null; }
                ISheet sheet = workbook.GetSheetAt(0);

                //表头  
                IRow header = sheet.GetRow(sheet.FirstRowNum);
                List<int> columns = new List<int>();
                for (int i = 0; i < header.LastCellNum; i++)
                {
                    object obj = GetValueTypeForXLSX(header.GetCell(i) as XSSFCell);// GetValueType(header.GetCell(i));
                    if (obj == null || obj.ToString() == string.Empty)
                    {
                        dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                    }
                    else
                        dt.Columns.Add(new DataColumn(obj.ToString()));
                    columns.Add(i);
                }
                //数据  
                for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
                {
                    DataRow dr = dt.NewRow();
                    bool hasValue = false;
                    foreach (int j in columns)
                    {
                        dr[j] = GetValueTypeForXLSX(sheet.GetRow(i).GetCell(j) as XSSFCell);// GetValueType(sheet.GetRow(i).GetCell(j));
                        if (dr[j] != null && dr[j].ToString() != string.Empty)
                        {
                            hasValue = true;
                        }
                    }
                    if (hasValue)
                    {
                        dt.Rows.Add(dr);
                    }
                }
            }
            return dt;
        }


        /// <summary>
        /// 获取单元格类型(xlsx)
        /// </summary>
        /// <param name="cell"></param>
        /// <returns></returns>
        private static object GetValueTypeForXLSX(XSSFCell cell)
        {
            if (cell == null)
                return null;
            switch (cell.CellType)
            {
                case CellType.Blank: //BLANK:
                    return null;
                case CellType.Boolean: //BOOLEAN:
                    return cell.BooleanCellValue;
                case CellType.Numeric: //NUMERIC:
                    return cell.DateCellValue;

                //case CellType.Numeric: //NUMERIC:
                //    return cell.NumericCellValue;

                case CellType.String: //STRING:
                    return cell.StringCellValue;
                case CellType.Error: //ERROR:
                    return cell.ErrorCellValue;
                case CellType.Formula: //FORMULA:
                default:
                    return "=" + cell.CellFormula;
            }
        }


    }