C#通过NPOI操作Excel的实例代码

public class ExcelHelper  {    /// <summary>    /// 根据Excel和Sheet返回DataTable    /// </summary>    /// <param name="filePath">Excel文件地址</param>    /// <param name="sheetIndex">Sheet索引</param>    /// <returns>DataTable</returns>    public static DataTable GetDataTable(string filePath, int sheetIndex)    {      return GetDataSet(filePath, sheetIndex).Tables[0];    }    /// <summary>    /// 根据Excel返回DataSet    /// </summary>    /// <param name="filePath">Excel文件地址</param>    /// <param name="sheetIndex">Sheet索引，可选，默认返回所有Sheet</param>    /// <returns>DataSet</returns>    public static DataSet GetDataSet(string filePath, int? sheetIndex = null)    {      DataSet ds = new DataSet();      IWorkbook fileWorkbook;      using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))      {        if (filePath.Last() == 's')        {          try          {            fileWorkbook = new HSSFWorkbook(fs);          }          catch (Exception ex)          {            throw ex;          }        }        else        {          try          {            fileWorkbook = new XSSFWorkbook(fs);          }          catch          {            fileWorkbook = new HSSFWorkbook(fs);          }        }      }      for (int i = 0; i < fileWorkbook.NumberOfSheets; i++)      {        if (sheetIndex != null && sheetIndex != i)          continue;        DataTable dt = new DataTable();        ISheet sheet = fileWorkbook.GetSheetAt(i);        //表头        IRow header = sheet.GetRow(sheet.FirstRowNum);        List<int> columns = new List<int>();        for (int j = 0; j < header.LastCellNum; j++)        {          object obj = GetValueTypeForXLS(header.GetCell(j) as HSSFCell);          if (obj == null || obj.ToString() == string.Empty)          {            dt.Columns.Add(new DataColumn("Columns" + j.ToString()));          }          else            dt.Columns.Add(new DataColumn(obj.ToString()));          columns.Add(j);        }        //数据        IEnumerator rows = sheet.GetEnumerator();        while (rows.MoveNext())        {          int j = sheet.FirstRowNum + 1;          DataRow dr = dt.NewRow();          bool hasValue = false;          foreach (int K in columns)          {            dr[K] = GetValueTypeForXLS(sheet.GetRow(K).GetCell(K) as HSSFCell);            if (dr[K] != null && dr[K].ToString() != string.Empty)            {              hasValue = true;            }          }          if (hasValue)          {            dt.Rows.Add(dr);          }          j++;        }        ds.Tables.Add(dt);      }      return ds;    }    /// <summary>    /// 根据DataTable导出Excel    /// </summary>    /// <param name="dt">DataTable</param>    /// <param name="file">保存地址</param>    public static void GetExcelByDataTable(DataTable dt, string file)    {      DataSet ds = new DataSet();      ds.Tables.Add(dt);      GetExcelByDataSet(ds, file);    }    /// <summary>    /// 根据DataSet导出Excel    /// </summary>    /// <param name="ds">DataSet</param>    /// <param name="file">保存地址</param>    public static void GetExcelByDataSet(DataSet ds, string file)    {      IWorkbook fileWorkbook = new HSSFWorkbook();      int index = 0;      foreach (DataTable dt in ds.Tables)      {        index++;        ISheet sheet = fileWorkbook.CreateSheet("Sheet" + index);        //表头        IRow row = sheet.CreateRow(0);        for (int i = 0; i < dt.Columns.Count; 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; j++)          {            ICell cell = row1.CreateCell(j);            cell.SetCellValue(dt.Rows[i][j].ToString());          }        }      }      //转为字节数组      MemoryStream stream = new MemoryStream();      fileWorkbook.Write(stream);      var buf = stream.ToArray();      //保存为Excel文件      using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))      {        fs.Write(buf, 0, buf.Length);        fs.Flush();      }    }    /// <summary>    /// 根据单元格将内容返回为对应类型的数据    /// </summary>    /// <param name="cell">单元格</param>    /// <returns>数据</returns>    private static object GetValueTypeForXLS(HSSFCell 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.NumericCellValue;        case CellType.String: //STRING:          return cell.StringCellValue;        case CellType.Error: //ERROR:          return cell.ErrorCellValue;        case CellType.Formula: //FORMULA:        default:          return "=" + cell.CellFormula;      }    }  }