NOPI导入XLS或XLSX文件

public class ExcelBase
    {
        public List<TModel> ImportData<TModel>(Stream stream, string templatePath,string fileName,  int begin = 2) where TModel : class, new()
        {
            IWorkbook workbook = null;
            if(fileName.ToLower().EndsWith(".xlsx"))
                workbook= new XSSFWorkbook(stream);
            else
                workbook = new HSSFWorkbook(stream);

            ISheet sheet = workbook.GetSheetAt(0);

            List<TModel> lst = new List<TModel>();

            int rowNum = sheet.LastRowNum;
            bool flag = true;
            for (int i = begin; i <= rowNum; i++)//第一行为标题，第二行为列名，不进行取数据
            {
                flag = true;
                TModel model = ExcelUtil.CreateFromExcel<TModel>(templatePath, (column, symbol) =>//symbol：2日期时间格式
                {
                    try
                    {
                        object value = null;
                        ICell cell = sheet.GetRow(i).GetCell(column);

                        if (cell != null)
                        {
                            if (symbol == 2)//日期时间格式
                            {
                                if (cell.CellType == CellType.Blank)
                                    return null;
                                DateTime time;
                                if (cell.CellType == CellType.Numeric)
                                {
                                    if (DateUtil.IsValidExcelDate(cell.NumericCellValue))
                                    {
                                        time = cell.DateCellValue;
                                    }
                                    else
                                    {
                                        time = DateUtil.GetJavaDate(cell.NumericCellValue);
                                    }
                                }
                                else if (cell.CellType == CellType.String)
                                {
                                    time = DateTime.Parse(cell.StringCellValue);
                                }
                                else if (cell.CellType == CellType.Formula)
                                {
                                    time = DateTime.Parse(cell.NumericCellValue.ToString());
                                }
                                else
                                {
                                    time = DateTime.Parse(cell.ToString());
                                }

                                return time;
                            }
                            else
                            {
                                switch (cell.CellType)
                                {
                                    case CellType.Boolean:
                                        {
                                            value = cell.BooleanCellValue;
                                            break;
                                        }
                                    case CellType.Numeric:
                                        {
                                            DecimalFormat df = new DecimalFormat("#.#####");
                                            System.Globalization.CultureInfo cf = new System.Globalization.CultureInfo("ZH-CN", true);
                                            value = df.Format(cell.NumericCellValue, cf);

                                            //value = cell.NumericCellValue;
                                            break;
                                        }
                                    case CellType.String:
                                        {
                                            value = cell.StringCellValue ?? string.Empty;
                                            break;
                                        }
                                    case CellType.Formula:
                                        {
                                            value = cell.NumericCellValue.ToString() ?? string.Empty;
                                            break;
                                        }
                                    default:
                                        {
                                            value = cell.ToString();
                                            break;
                                        }
                                }
                            }
                        }
                        return value;
                    }
                    catch (Exception ex)
                    {
                        flag = false;
                        return null;
                    }
                }, rowNum);

                if (!flag)
                {
                    //errorList.Add(model);
                }
                else if (model != null)
                {
                    lst.Add(model);
                }
                else
                {
                    continue;
                }
            }
            return lst;
        }
    }