关于Npoi+excel文件读取，修改文件内容的处理方式

因最近有需求场景，实现对文件的读写操作，又不单独生成新的文件，对于源文件的修改，做了一个简单实现，如下↓

---

 // 要操作的excel文件路径
             string fileName = Server.MapPath("~/Content/test.xlsx");
             if (!System.IO.File.Exists(fileName)) return Content("文件不存在！");
             IWorkbook workbook;

             //把文件内容导入到工作薄当中，然后关闭文件
             FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.ReadWrite);

             workbook = WorkbookFactory.Create(fs);
             fs.Close();//编辑工作薄当中内容
             ISheet sheet = workbook.GetSheetAt();

             //workbook.GetSheetAt(0).GetRow(0).Cells[0].SetCellValue("TestCell");
             for (int i = ; i <= sheet.LastRowNum; i++)
             {
                 foreach (ICell cell in sheet.GetRow(i).Cells)
                 {
                     cell.SetCellType(cell.CellType);
                     if (cell.CellType == CellType.Numeric)
                     {
                         if (HSSFDateUtil.IsCellDateFormatted(cell))//日期类型
                         {
                             cell.SetCellValue(cell.DateCellValue.ToString());
                         }
                         else//其他数字类型
                         {
                             cell.SetCellValue(cell.NumericCellValue.ToString());
                         }
                     }
                     else
                     {
                         cell.SetCellValue(cell.StringCellValue.ToString());
                     }
                 }
                 if (i != )
                 {
                     ICell firstCell = sheet.GetRow(i).Cells[];
                     firstCell.SetCellType(firstCell.CellType);
                     var cellValue = firstCell.StringCellValue.ToDecimal().ToString();
                     firstCell.SetCellValue(cellValue);
                 }
             }

             //把编辑过后的工作薄重新保存为excel文件
             FileStream fs2 = System.IO.File.Create(fileName);
             workbook.Write(fs2);
             fs2.Close();
             return Content("操作成功！！" + DateTime.Now);

读取文件内容更新文件状态

 // 要操作的excel文件路径
             string fileName = Server.MapPath("~/Content/test.xlsx");
             if (!System.IO.File.Exists(fileName)) return Content("文件不存在,请检查路径及文件名称是否正确！");
             //IWorkbook workbook;
             //把文件内容导入到工作薄当中，然后关闭文件
             //FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.ReadWrite);
             //workbook = WorkbookFactory.Create(fs);
             //fs.Close();//编辑工作薄当中内容
             //如果是xls，使用HSSFWorkbook；如果是xlsx，使用XSSFWorkbook
             XSSFWorkbook xssFWorkbook;
             using (FileStream file = new FileStream(fileName, FileMode.Open, FileAccess.ReadWrite))
             {
                 xssFWorkbook = new XSSFWorkbook(file);
             }

             ISheet sheet = xssFWorkbook.GetSheetAt();
             var userList = GetUserLists(sheet);
             var userNames = userList.Select(u =>
             {
                 return u.UserName.Replace(u.UserName, $"'{u.UserName}'");
             });
             var companyNames = userList.Select(u =>
             {
                 return u.CompanyName.Replace(u.CompanyName, $"'{u.CompanyName}'");
             });

             var userIdCards = userList.Select((u, i) =>
              {
                  return $" SELECT '{u.UserName}' AS UserName,'{u.CompanyName}' AS CompanyName,'{u.LegalPersonIdNumber}' AS LegalPersonIdNumber ";
              });
             var dataList = AsyncHelper.RunSync(() => _userIdFileAppService.RunSearchAndUpdateData(
                 new UserIdentityCardInput
                 {
                     UserNameString = string.Join(",", userNames),
                     CompanyNameString = string.Join(",", companyNames),
                     UserIdCardString = string.Format(@"SELECT * INTO #tbUserIdCardTable FROM ( {0} ) a;", string.Join("  UNION  ", userIdCards))
                 }
                 ));
             for (int i = ; i <= sheet.LastRowNum; i++)
             {
                 if (i != )
                 {
                     var userName = sheet.GetRow(i).Cells[].ToString();
                     var companyName = sheet.GetRow(i).Cells[].ToString();
                     //添加列
                     ICell lastCell = sheet.GetRow(i).CreateCell();
                     lastCell.SetCellType(lastCell.CellType);
                     ICellStyle newStyle = xssFWorkbook.CreateCellStyle();
                     //XSSFCellStyle styleTemp = ((XSSFCellStyle)newStyle);
                     //HSSFPalette palette = xssFWorkbook.GetCustomPalette();

                     if (dataList.Find(a => a.UserName == userName && a.CompanyName == companyName) != null)
                     {
                         lastCell.SetCellValue("已更新");
                         //Color c = Color.FromArgb(98, 185, 106);
                         //palette.SetColorAtIndex((short)9, c.R, c.G, c.B);
                         //var color = palette.FindColor(c.R, c.G, c.B);
                         //newStyle.FillPattern = FillPattern.SolidForeground;
                         //newStyle.FillForegroundColor = color.Indexed;

                         XSSFColor color = new XSSFColor();
                         color.SetRgb(new byte[] { , ,  });
                         newStyle.FillPattern = FillPattern.SolidForeground;
                         newStyle.FillForegroundColor = ;
                     }
                     else
                     {
                         lastCell.SetCellValue("未更新");
                         //创建字体
                         XSSFFont ffont = (XSSFFont)xssFWorkbook.CreateFont();
                         XSSFColor color = new XSSFColor();
                         color.SetRgb(new byte[] { , ,  });
                         //给字体设置颜色
                         ffont.Color = color.Indexed;
                         //给样式添加字体
                         newStyle.SetFont(ffont);

                         newStyle.FillPattern = FillPattern.SolidForeground;
                         newStyle.FillForegroundColor = ;

                     }
                     lastCell.CellStyle = newStyle;
                 }
             }

             //把编辑过后的工作薄重新保存为excel文件
             FileStream fs2 = System.IO.File.Create(fileName);
             xssFWorkbook.Write(fs2);
             fs2.Close();
             return Content("操作成功！！" + DateTime.Now);