//创建工作表
            HSSFWorkbook workbook = new HSSFWorkbook();
            Sheet sheet = workbook.CreateSheet("Sheet1");

            //创建表头
            Row headerRow = sheet.CreateRow(1);
            for (int i = 0; i < strField.Length; i++)
            {
                headerRow.CreateCell(i).SetCellValue(strField[i]);
            }

            //创建内容
            int rowIndex = 2;
            Row dataRow = sheet.CreateRow(rowIndex);
            for (int i = 0; i < list.Count;i++ )
            {
                Cell newCell = dataRow.CreateCell(i);
                newCell.SetCellValue(list[i]);
            }
            rowIndex++;

            FileStream file = new FileStream(@"c:/test.xls", FileMode.Create);
            workbook.Write(file);
            file.Close();

DataTable生成EXCEL:

public static void getExcel(DataTable dt)
        {
            NPOI.HSSF.UserModel.HSSFWorkbook book = new NPOI.HSSF.UserModel.HSSFWorkbook();
            NPOI.SS.UserModel.Sheet sheet = book.CreateSheet("test_01");
            NPOI.SS.UserModel.Row row = sheet.CreateRow(0);

            //创建表头
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                row.CreateCell(i).SetCellValue(dt.Columns[i].ColumnName);
            }

            //创建内容
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                NPOI.SS.UserModel.Row row2 = sheet.CreateRow(i + 1);
                for (int j = 0; j < dt.Columns.Count; j++)
                    row2.CreateCell(j).SetCellValue(dt.Rows[i][j].ToString());
            }


            //写入到客户端
            FileStream file = new FileStream(@"c:/test2.xls", FileMode.Create);
            book.Write(file);
            file.Close();
            book.Dispose();
        }

读取excel模板生成EXCEL：

            FileStream file = new FileStream(@"c:/book1.xls", FileMode.Open, FileAccess.Read);

            HSSFWorkbook hssfworkbook = new HSSFWorkbook(file);
            Sheet sheet1 = hssfworkbook.GetSheet("Sheet1");
            sheet1.GetRow(1).GetCell(1).SetCellValue(200200);
            sheet1.GetRow(2).GetCell(1).SetCellValue(300);
            sheet1.GetRow(3).GetCell(1).SetCellValue(500050);
            sheet1.GetRow(4).GetCell(1).SetCellValue(8000);
            sheet1.GetRow(5).GetCell(1).SetCellValue(110);
            sheet1.GetRow(6).GetCell(1).SetCellValue(100);
            sheet1.GetRow(7).GetCell(1).SetCellValue(200);
            sheet1.GetRow(8).GetCell(1).SetCellValue(210);
            sheet1.GetRow(9).GetCell(1).SetCellValue(2300);
            sheet1.GetRow(10).GetCell(1).SetCellValue(240);
            sheet1.GetRow(11).GetCell(1).SetCellValue(180123);
            sheet1.GetRow(12).GetCell(1).SetCellValue(150);

            //Force excel to recalculate all the formula while open
            sheet1.ForceFormulaRecalculation = true;
            FileStream file2 = new FileStream(@"c:/testadsafd.xls", FileMode.Create);
            hssfworkbook.Write(file2);
            file.Close();
            file2.Close();