导出数据到Excel

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Data;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using NPOI.HSSF.UserModel;

namespace ConsoleApplication5
{
    class ExcelHelper
    {
        private string fileName = null;
        private IWorkbook workbook = null;
        private FileStream fs = null;
        private bool disposed;

        public ExcelHelper()
        {}

        public ExcelHelper(string filename)
        {
            this.fileName = filename;
            disposed = false;
        }
        #region 把Datatable数据导入Excel文件
        /// <summary>
        /// 把Datatable数据导入Excel文件
        /// </summary>
        /// <param name="data">表</param>
        /// <param name="sheetName">sheet的名称</param>
        /// <param name="isColumnWritten">是否导入列名</param>
        /// <returns></returns>
        public int DataTableToExcel(DataTable data, string sheetName, bool isColumnWritten)
        {
            int i = 0;
            int j = 0;
            int count = 0;
            ISheet sheet = null;
            //判断是否存在该文件
            if (File.Exists("../../IntroductionToExcel/"+fileName) == false)
            {
                //创建文件
                File.Create("../../IntroductionToExcel/" + fileName).Close();
            }
            
            fs = new FileStream("../../IntroductionToExcel/"+fileName, FileMode.Open, FileAccess.ReadWrite);
            fs.Position=0;
            //判断Excel版本
            if (fileName.IndexOf(".xlsx") > 0)//2007版本
            {
                workbook = new XSSFWorkbook();
            }
            else if (fileName.IndexOf(".xls") > 0)//2003版本
            {
                workbook = new HSSFWorkbook();
            }

            try
            {
                if (workbook != null)
                {
                    sheet = workbook.CreateSheet(sheetName);//创建sheet
                }
                else
                {
                    return -1;
                }

                if (isColumnWritten)//是否导入列名
                {
                    IRow row = sheet.CreateRow(0);//第一行，索引从0开始
                    for (j = 0; j < data.Columns.Count; j++)
                    {
                        row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);//导入列名
                    }
                    count = 1;
                }
                else
                {
                    count = 0;
                }

                for (i = 0; i < data.Rows.Count; i++)//循环行
                {
                    IRow row = sheet.CreateRow(count);
                    for (j = 0; j < data.Columns.Count; j++)//循环列
                    {
                        row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());//当前单元格data.Rows[i][j]
                    }
                    ++count;
                }
                workbook.Write(fs);
                return count;//返回导入行数
            }
            catch
            {
                return -1;
            }
        } 
        #endregion

    }
}