自用ExecelHelper.cs

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

namespace PaperTool.DAL
{
    class ExcelHelper
    {
        public static DataTable ExcelToDataTable(string excelPath)
        {
            DataTable dt = new DataTable();
            using (Stream stream = File.OpenRead(excelPath))
            {
                HSSFWorkbook workbook = new HSSFWorkbook(stream);
                ISheet sheet = workbook.GetSheetAt(0);
                IRow rowheader = sheet.GetRow(0);
                foreach (ICell cell in rowheader)
                {
                    dt.Columns.Add(cell.ToString());
                }
                for (int i = sheet.FirstRowNum + 1; i < =sheet.LastRowNum; i++)
                {
                    DataRow dr = dt.NewRow();
                    IRow irow = sheet.GetRow(i);
                    for (int j = irow.FirstCellNum; j < irow.LastCellNum; j++)
                    {
                        dr[j] = irow.GetCell(j).ToString();
                    }
                    dt.Rows.Add(dr);
                }
                return dt;
            }
        }

        public static void WriteExecel(DataTable dt,string path)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            ISheet sheet = workbook.CreateSheet();
            IRow rowheader = sheet.CreateRow(0);
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                rowheader.CreateCell(i, CellType.STRING).SetCellValue(dt.Columns[i].ColumnName);
            }
            for (int rowid = 0; rowid < dt.Rows.Count; rowid++)
            {
                DataRow row = dt.Rows[rowid];
                IRow irow = sheet.CreateRow(rowid + 1);
                for (int columnid = 0; columnid < dt.Columns.Count; columnid++)
                {
                    irow.CreateCell(columnid, CellType.STRING).SetCellValue(row[columnid].ToString());
                }
            }
            
            using (Stream stream = File.OpenWrite(path))
            {
                workbook.Write(stream);
            }
        }
    }
}