利用NPOI导出excel

using NPOI;
using NPOI.POIFS;
using NPOI.HPSF;
using NPOI.HSSF;
using NPOI.HSSF.UserModel;
using NPOI.HSSF.Util;
using NPOI.Util;
using NPOI.SS.UserModel;
using NPOI.SS.Util;

//导出为excel
private void OutputExcel(List<SalaryDataClass> datas, string headerTxt, string fileName)
    {
        HttpContext curContent = HttpContext.Current;

        curContent.Response.ContentType = "application/vnd.ms-excel";
        curContent.Response.ContentEncoding = Encoding.UTF8;
        curContent.Response.Charset = "";
        curContent.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName, Encoding.UTF8));
        byte[] buff = Export(datas, headerTxt).GetBuffer();
        curContent.Response.BinaryWrite(buff);
        curContent.Response.End();
    }

  private MemoryStream Export(List<SalaryDataClass> datas, string headerTxt)
    {
        HSSFWorkbook workbook = new HSSFWorkbook();
      
        HSSFCellStyle dateStyle =(HSSFCellStyle) workbook.CreateCellStyle();
        dateStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.CENTER;
        dateStyle.VerticalAlignment = NPOI.SS.UserModel.VerticalAlignment.CENTER;
        HSSFFont font =(HSSFFont) workbook.CreateFont();
        font.FontHeightInPoints=11;
        font.FontName = "宋体";
        dateStyle.SetFont(font);

        HSSFDataFormat format =(HSSFDataFormat) workbook.CreateDataFormat();
        dateStyle.DataFormat = format.GetFormat("yyyy-MM-dd");
        //列宽
        int[] arrCountWidth = new int[6];
        foreach (var item in datas)//此处填充表格实体内容，根据需要写
        {
            HSSFSheet sheet = (HSSFSheet)workbook.CreateSheet(item.EmpName+Year+Month+"单");
            //表头
            HSSFRow headerRow = (HSSFRow)sheet.CreateRow(0);
            HSSFCell cell=(HSSFCell) headerRow.CreateCell(0);
            cell.SetCellValue("测试测试");
            cell.CellStyle = dateStyle;              
            Merge(sheet, 0, 0, 1, 3);
            HSSFCell dateCell = (HSSFCell)headerRow.CreateCell(4);
            dateCell.SetCellValue("日期：" + Year + "-" + Month ); ;
            dateCell.CellStyle = dateStyle;
            Merge(sheet, 0, 4, 1, 5);
          
          
            dateCell = (HSSFCell)secRow.CreateCell(4);
            dateCell.CellStyle = dateStyle;
            dateCell.SetCellValue(item.Depart);
            Merge(sheet, 4, 4, 4, 5);

            HSSFRow basicRow = (HSSFRow)sheet.CreateRow(7);
            basicRow.CreateCell(0).SetCellValue("列名");
            basicRow.GetCell(0).CellStyle = dateStyle;
            basicRow.CreateCell(1).SetCellValue(item.BasicSa);
            basicRow.GetCell(1).CellStyle = dateStyle;                   
            
            SetWidth(sheet);
        }
        using (MemoryStream ms = new MemoryStream())
        {
            workbook.Write(ms);
            ms.Flush();
            ms.Position = 0;
            return ms;
        }
    }

 /// <summary>
    /// 合并单元格
    /// </summary>
    /// <param name="r1">左上角单元格行标(从0开始，下同)</param>
    /// <param name="c1">左上角单元格列标</param>
    /// <param name="r2">右下角单元格行标</param>
    /// <param name="c2">右下角单元格列标</param>
    private void Merge(HSSFSheet sheet, int r1, int c1, int r2, int c2)
    {
        CellRangeAddress cellRange=new CellRangeAddress(r1, r2, c1, c2);
        sheet.AddMergedRegion(cellRange);
    }

 private void SetWidth(HSSFSheet sheet)
    {
        for (int col = 0; col <= 6; col++)
        {
            sheet.AutoSizeColumn(col);
            int colWidth = sheet.GetColumnWidth(col) / 256;
            for (int rowNum = 1; rowNum <= sheet.LastRowNum; rowNum++)
            {
                HSSFRow currentRow;
                if (sheet.GetRow(rowNum) == null)
                    currentRow = (HSSFRow)sheet.CreateRow(rowNum);
                else
                    currentRow = (HSSFRow)sheet.GetRow(rowNum);
                if (currentRow.GetCell(col) != null)
                {
                    HSSFCell currentCell = (HSSFCell)currentRow.GetCell(col);
                    int length = Encoding.Default.GetBytes(currentCell.ToString()).Length;
                    if (colWidth < length)
                        colWidth = length;
                }
            }
            sheet.SetColumnWidth(col, colWidth*256);
        }
    }