问NPOI -保存到文件后损坏.xlsx工作簿

EN

[Authorize]
public void ExportUsers()
{
    var path = Server.MapPath(@"~\Content\ExportTemplates\") + "sample.xlsx";

    FileStream sw = new FileStream(path, FileMode.Open, FileAccess.Read);

    IWorkbook workbook = WorkbookFactory.Create(sw);       

    ISheet sheet = workbook.GetSheetAt(0);
    IRow row = sheet.GetRow(12);

    ICell cell = row.CreateCell(row.LastCellNum);
    cell.SetCellValue("test");
    workbook.CreateSheet("Ripon");            
    sw.Close();

    using (var exportData = new MemoryStream())
    {
        workbook.Write(exportData);
        string saveAsFileName = string.Format("Export-{0:d}.xls", DateTime.Now).Replace("/", "-");
        System.Web.HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
        System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", saveAsFileName));
        System.Web.HttpContext.Current.Response.Clear();
        System.Web.HttpContext.Current.Response.BinaryWrite(exportData.GetBuffer());
        System.Web.HttpContext.Current.Response.End();                    
    }
}