c# NPOI 导入和导出EXCEL

using NPOI.HSSF.UserModel;
using NPOI.HSSF.Util;
using NPOI.SS.Formula.Functions;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Reflection;
using System.Text;
using System.Windows.Forms;

namespace TestNPOI
{
    public partial class Form1 : Form
    {
        public Form1（）
        {
            InitializeComponent（）;
        }



        public static DataTable GetDS（string fileName bool isFirstRowColumn）
        {
            IWorkbook workbook = null;
            FileStream fs = null;
            bool disposed;
            ISheet sheet = null;
            string sheetName = null;
            DataTable data = new DataTable（）;
            int startRow = 0;
            try
            {
                fs = new FileStream（fileName FileMode.Open FileAccess.Read）;
                if （fileName.IndexOf（“.xlsx“） > 0） // 2007版本
                    workbook = new XSSFWorkbook（fs）;
                else if （fileName.IndexOf（“.xls“） > 0） // 2003版本
                    workbook = new HSSFWorkbook（fs）;


                if （sheetName != null）
                {
                    sheet = workbook.GetSheet（sheetName）;
                    if （sheet == null） //如果没有找到指定的sheetName对应的sheet，则尝试获取第一个sheet
                    {
                        sheet = workbook.GetSheetAt（0）;
                    }
                }
                else
                {
                    sheet = workbook.GetSheetAt（0）;
                }
                if （sheet != null）
                {
                    IRow firstRow = sheet.GetRow（7）;
                    int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数

                    if （isFirstRowColumn）
                    {
                        for （int i = firstRow.FirstCellNum; i < cellCount; ++i）
                        {
                            ICell cell = firstRow.GetCell（i）;
                            if （cell != null）
                            {
                                string cellValue = cell.StringCellValue;
                                if （cellValue != null）
                                {
                                    DataColumn column = new DataColumn（cellValue）;
                                    data.Columns.Add（column）;
                                }
                            }
                        }
                        startRow = sheet.FirstRowNum + 1;
                    }
                    else
                    {
                        startRow = sheet.FirstRowNum;
                    }

                    //最后一列的标号
                    int rowCount = sheet.LastRowNum;
                    for （int i = startRow; i <= rowCount; ++i）
                    {
                        IRow row = sheet.GetRow（i）;