using NPOI.SS.UserModel;   using NPOI.HSSF.UserModel;     //创建Execl  IWorkbook hssfworkbook =new HSSFWorkbook();     //创建一个Sheet  hssfworkbook.CreateSheet("Sheet1");     //HSSFWorkbook实例写入文件  FileStream file = new FileStream(@"test.xls", FileMode.Create);   hssfworkbook.Write(file);   file.Close();       //要创建单元格首先要创建单元格所在的行，比如，下面的代码创建了第0行：   ISheet sheet1 = hssfworkbook.CreateSheet("Sheet1");   IRow row1=sheet1.CreateRow(0);     //行建好了，就可以建单元格了，比如创建A1位置的单元格：   row1.CreateCell(0).SetCellValue("This is a Sample");     //或者sheet1.GetRow(0).CreateCell(0).SetCellValue("This is a Sample");       //set header text 设置页眉  s1.Header.Center = "This is a test sheet";   //set footer text 设置页脚  s1.Footer.Left = "Copyright NPOI Team";   s1.Footer.Right = "created by 123";     //set date format 设置单元格格式  ICellStyle cellStyle = hssfworkbook.CreateCellStyle();  IDataFormat format = hssfworkbook.CreateDataFormat();   cellStyle.DataFormat = format.GetFormat("yyyy年m月d日");  //cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("0.00"); 单元格格式为“0.00”来表示,"￥#,##0"美元显示,"0.00%"百分比显示  cell.CellStyle=cellStyle;    //合并单元格  IRow row = sheet.CreateRow(0);   ICell cell = row.CreateCell(0);   cell.SetCellValue("Sales Report");   ICellStyle style = hssfworkbook.CreateCellStyle();   style.Alignment = HorizontalAlignment.CENTER;   IFont font = hssfworkbook.CreateFont();   font.FontHeight = 20*20;   style.SetFont(font);   cell.CellStyle = style;  sheet.AddMergedRegion(new Region(0, 0, 0, 5)); 

NPOI格式设置1