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 = ;
             int j = ;
             int count = ;
             ISheet sheet = null;
             IWorkbook workbook = null;
             using (FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite))
             {
                 if (!blnAppled)
                 {
                     if (fileName.IndexOf(".xlsx") > ) // 2007版本
                         workbook = new XSSFWorkbook();
                     else if (fileName.IndexOf(".xls") > ) // 2003版本
                         workbook = new HSSFWorkbook();
                 }
                 else
                 {
                     if (fileName.IndexOf(".xlsx") > ) // 2007版本
                         workbook = new XSSFWorkbook(fs);
                     else if (fileName.IndexOf(".xls") > ) // 2003版本
                         workbook = new HSSFWorkbook(fs);
                 }

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

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

                     count = sheet.LastRowNum + ;

                     for (i = ; i < data.Rows.Count; ++i)
                     {
                         IRow row = sheet.CreateRow(count);
                         for (j = ; j < data.Columns.Count; ++j)
                         {
                             row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());
                         }
                         ++count;
                     }

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

             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 = ;
             IWorkbook workbook = null;
             try
             {
                 FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                 if (fileName.IndexOf(".xlsx") > ) // 2007版本
                     workbook = new XSSFWorkbook(fs);
                 else if (fileName.IndexOf(".xls") > ) // 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();
                     }
                 }
                 else
                 {
                     sheet = workbook.GetSheetAt();
                 }
                 if (sheet != null)
                 {
                     IRow firstRow = sheet.GetRow();
                     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 + ;
                     }
                     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 = ; i < ; i++)
             {
                 DataRow dr = dt.NewRow();
                 for (int j = ; j < ; j++)
                 {
                     dr[j] = "1_" + i.ToString() + "_" + j.ToString();
                 }
                 dt.Rows.Add(dr);
             }
             ExcelEX.DataTableToExcel("d:\\123.xlsx",dt);
             dt.Rows.Clear();

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

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

看结果