C#使用NOPI库实现导入Excel文档

  /// <summary>
  /// 根据Excel格式读取Excel
  /// </summary>
  /// <param name="stream">文件流</param>
  /// <param name="type">Excel格式枚举类型，xls/xlsx</param>
  /// <param name="sheetName">表名，默认取第一张</param>
  /// <returns>DataTable</returns>
  private static DataTable ImportExcel(Stream stream, ExcelExtType type, string sheetName)
  {
    DataTable dt = new DataTable();
    IWorkbook workbook;
    try
    {
      //xls使用HSSFWorkbook类实现，xlsx使用XSSFWorkbook类实现
      switch (type)
      {
        case ExcelExtType.xlsx:
          workbook = new XSSFWorkbook(stream);
          break;
        default:
          workbook = new HSSFWorkbook(stream);
          break;
      }
      ISheet sheet = null;
      //获取工作表 默认取第一张
      if (string.IsNullOrWhiteSpace(sheetName))
        sheet = workbook.GetSheetAt(0);
      else
        sheet = workbook.GetSheet(sheetName);

      if (sheet == null)
        return null;
      IEnumerator rows = sheet.GetRowEnumerator();
      #region 获取表头
      IRow headerRow = sheet.GetRow(0);
      int cellCount = headerRow.LastCellNum;
      for (int j = 0; j < cellCount; j++)
      {
        ICell cell = headerRow.GetCell(j);
        if (cell != null)
        {
          dt.Columns.Add(cell.ToString());
        }
        else
        {
          dt.Columns.Add("");
        }
      }
      #endregion
      #region 获取内容
      for (int i = (sheet.FirstRowNum + 1); i <= sheet.LastRowNum; i++)
      {
        IRow row = sheet.GetRow(i);
        DataRow dataRow = dt.NewRow();

        for (int j = row.FirstCellNum; j < cellCount; j++)
        {
          if (row.GetCell(j) != null)
          {
            //判断单元格是否为日期格式
            if (row.GetCell(j).CellType == NPOI.SS.UserModel.CellType.Numeric && HSSFDateUtil.IsCellDateFormatted(row.GetCell(j)))
            {
              if (row.GetCell(j).DateCellValue.Year >=1970)
              {
                dataRow[j] = row.GetCell(j).DateCellValue.ToString();
              }
              else
              {
                dataRow[j] = row.GetCell(j).ToString();

              }
            }
            else
            {
              dataRow[j] = row.GetCell(j).ToString();
            }
          }
        }
        dt.Rows.Add(dataRow);
      }
      #endregion

    }
    catch (Exception ex)
    {
      dt=null;
    }
    finally
    {
      //if (stream != null)
      //{
      //  stream.Close();
      //  stream.Dispose();
      //}
    }
    return dt;
  }

  /// <summary>
  /// 上传Excel导入
  /// </summary>
  /// <param name="file">上载文件对象</param>
  /// <param name="errorMsg">错误信息</param>
  /// <param name="sheetName">表名，默认取第一张</param>
  /// <returns></returns>
  public static DataTable Import(System.Web.HttpPostedFileBase file, ref string errorMsg, string sheetName = "")
  {
    if (file == null || file.InputStream == null || file.InputStream.Length == 0)
    {
      errorMsg = "请选择要导入的Excel文件";
      return null;
    }
    var excelType = GetExcelFileType(file.FileName);
    if (excelType == null)
    {
      errorMsg = "请选择正确的Excel文件";
      return null;
    }
    using (var stream = new MemoryStream())
    {
      file.InputStream.Position = 0;
      file.InputStream.CopyTo(stream);
      var dt = ImportExcel(stream, excelType.Value, sheetName);
      if (dt == null)
        errorMsg = "导入失败,请选择正确的Excel文件";
      return dt;
    }
  }

  /// <summary>
  /// 根据文件路径导入Excel
  /// </summary>
  /// <param name="filePath"></param>
  /// <param name="errorMsg">错误信息</param>
  /// <param name="sheetName">表名，默认取第一张</param>
  /// <returns>可能为null的DataTable</returns>
  public static DataTable Import(string filePath, ref string errorMsg, string sheetName = "")
  {
    var excelType = GetExcelFileType(filePath);
    if (GetExcelFileType(filePath) == null)
    {
      errorMsg = "请选择正确的Excel文件";
      return null;
    }
    if (!File.Exists(filePath))
    {
      errorMsg = "没有找到要导入的Excel文件";
      return null;
    }
    DataTable dt;
    using (var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    {
      dt = ImportExcel(stream, excelType.Value, sheetName);
    }
    if (dt == null)
      errorMsg = "导入失败,请选择正确的Excel文件";
    return dt;
  }