使用NPOI导出，读取EXCEL（可追加功能）

使用NPOI导出，读取EXCEL，具有可追加功能

看代码

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

namespace NPOIExcel
{
    public class ExcelEX
    {

        /// <summary>
        /// 将DataTable数据导入到excel中
        /// </summary>
        /// <param name="fileName">文件名</param>
        /// <param name="data">要导入的数据</param>
        /// <param name="sheetName">要导入的excel的sheet的名称</param>
        /// <param name="blnAppled">是否是追加模式</param>
        /// <param name="isColumnWritten">DataTable的列名是否要导入</param>
        /// <returns>导入数据行数(包含列名那一行)</returns>
        public static int DataTableToExcel(string fileName, DataTable data, bool blnAppled = false, string sheetName = "sheet1", bool isColumnWritten = true)
        {
            int i = 0;
            int j = 0;
            int count = 0;
            ISheet sheet = null;
            IWorkbook workbook = null;
            using (FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite))
            {
                if (!blnAppled)
                {
                    if (fileName.IndexOf(".xlsx") > 0) // 2007版本
                        workbook = new XSSFWorkbook();
                    else if (fileName.IndexOf(".xls") > 0) // 2003版本
                        workbook = new HSSFWorkbook();
                }
                else
                {
                    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);
                }

                try
                {
                    if (!blnAppled && !string.IsNullOrEmpty(sheetName))
                    {
                        if (workbook != null)
                        {
                            sheet = workbook.CreateSheet(sheetName);
                        }
                        else
                        {
                            return -1;
                        }
                    }
                    else
                    {
                        sheet = workbook.GetSheetAt(0);
                    }

                    if (!blnAppled)
                    {
                        if (isColumnWritten == true) //写入DataTable的列名
                        {
                            IRow row = sheet.CreateRow(0);
                            for (j = 0; j < data.Columns.Count; ++j)
                            {
                                row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);
                            }
                            count = 1;
                        }
                        else
                        {
                            count = 0;
                        }
                    }

                    count = sheet.LastRowNum + 1;

                    for (i = 0; i < data.Rows.Count; ++i)
                    {
                        IRow row = sheet.CreateRow(count);
                        for (j = 0; j < data.Columns.Count; ++j)
                        {
                            row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());
                        }
                        ++count;
                    }
                   
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Exception: " + ex.Message);
                    return -1;
                }
            }

            FileStream outFs = new FileStream(fileName, FileMode.Open);
            workbook.Write(outFs);
            outFs.Close();            
            return count;
        }

        /// <summary>
        /// 将excel中的数据导入到DataTable中
        /// </summary>
        /// <param name="sheetName">excel工作薄sheet的名称</param>
        /// <param name="isFirstRowColumn">第一行是否是DataTable的列名</param>
        /// <returns>返回的DataTable</returns>
        public static DataTable ExcelToDataTable(string fileName, string sheetName = null, bool isFirstRowColumn = true)
        {
            ISheet sheet = null;
            DataTable data = new DataTable();
            int startRow = 0;
            IWorkbook workbook = null;
            try
            {
                FileStream 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(0);
                    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);
                        if (row == null) continue; //没有数据的行默认是null　　　　　　　

                        DataRow dataRow = data.NewRow();
                        for (int j = row.FirstCellNum; j < cellCount; ++j)
                        {
                            if (row.GetCell(j) != null) //同理，没有数据的单元格都默认是null
                                dataRow[j] = row.GetCell(j).ToString();
                        }
                        data.Rows.Add(dataRow);
                    }
                }

                return data;
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception: " + ex.Message);
                return null;
            }
        }


    }
}

看测试

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using NPOIExcel;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("A", typeof(string));
            dt.Columns.Add("B", typeof(string));
            dt.Columns.Add("C", typeof(string));
            for (int i = 0; i < 50; i++)
            {
                DataRow dr = dt.NewRow();
                for (int j = 0; j < 3; j++)
                {
                    dr[j] = "1_" + i.ToString() + "_" + j.ToString();
                }
                dt.Rows.Add(dr);
            }
            ExcelEX.DataTableToExcel("d:\123.xlsx",dt);
            dt.Rows.Clear();

            for (int i = 0; i < 50; i++)
            {
                DataRow dr = dt.NewRow();
                for (int j = 0; j < 3; j++)
                {
                    dr[j] = "2_" + i.ToString() + "_" + j.ToString();
                }
                dt.Rows.Add(dr);
            }

            ExcelEX.DataTableToExcel("d:\123.xlsx", dt,true);
            Console.ReadKey();
        }
    }
}

看结果