C#利用NPOI在同一个Excel文件中创建多个sheet

 private void buttonTest_Click(object sender, EventArgs e)
        {
            HSSFWorkbook workBook = new HSSFWorkbook();
            //ISheet sheetA = workBook.CreateSheet("sheetA");
            //ISheet sheetB = workBook.CreateSheet("sheetB");

            createSheet(workBook,"SheetA");
            createSheet(workBook,"SheetB");
            createSheet(workBook,"SheetC");

            string path = Application.StartupPath + @"\test.xls";
            if (File.Exists(path))
            {
                File.Delete(path);
            }
            using (FileStream file = new FileStream(path, FileMode.Create))
            {
                workBook.Write(file);　　//创建Excel文件。
                file.Close();
            }
            MessageBox.Show("OK");
        }

        private ISheet createSheet(HSSFWorkbook workBook, string sheetName)
        {
            ISheet sheet = workBook.CreateSheet(sheetName);
            IRow RowHead = sheet.CreateRow(0);

            for (int iColumnIndex = 0; iColumnIndex < 10; iColumnIndex++)
            {
                RowHead.CreateCell(iColumnIndex).SetCellValue(Guid.NewGuid().ToString());
            }

            for (int iRowIndex = 0; iRowIndex < 20; iRowIndex++)
            {
                IRow RowBody = sheet.CreateRow(iRowIndex + 1);
                for (int iColumnIndex = 0; iColumnIndex < 10; iColumnIndex++)
                {
                    RowBody.CreateCell(iColumnIndex).SetCellValue(DateTime.Now.Millisecond);
                    sheet.AutoSizeColumn(iColumnIndex);
                }
            }
            return sheet;
        }