这里有详细讲解优缺点

https://www.cnblogs.com/lychee/p/7273508.html

1.使用Office自带的库

需要用户机安装office

Microsoft.Office.Interop.Excel

using Microsoft.Office.Interop.Excel;
using Excel = Microsoft.Office.Interop.Excel;

        private void btn_Office_Click(object sender, EventArgs e)
        {
            string importExcelPath = "E:\\import.xlsx";
            string exportExcelPath = "E:\\export.xlsx";
            //创建
            Excel.Application xlApp = new Excel.Application();
            xlApp.DisplayAlerts = false;
            xlApp.Visible = false;
            xlApp.ScreenUpdating = false;
            //打开Excel
            Excel.Workbook xlsWorkBook = xlApp.Workbooks.Open(importExcelPath, System.Type.Missing, System.Type.Missing, System.Type.Missing,
            System.Type.Missing, System.Type.Missing, System.Type.Missing, System.Type.Missing, System.Type.Missing, System.Type.Missing, System.Type.Missing,
            System.Type.Missing, System.Type.Missing, System.Type.Missing, System.Type.Missing);

            //处理数据过程，更多操作方法自行百度
            Excel.Worksheet sheet = xlsWorkBook.Worksheets[1];//工作薄从1开始，不是0
            sheet.Cells[1, 1] = "test";

            //另存
            xlsWorkBook.SaveAs(exportExcelPath, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, XlSaveAsAccessMode.xlNoChange,
                Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
            //关闭Excel进程
            ClosePro(xlApp, xlsWorkBook);
        }

        public void ClosePro(Excel.Application xlApp, Excel.Workbook xlsWorkBook)
        {
            if (xlsWorkBook != null)
                xlsWorkBook.Close(true, Type.Missing, Type.Missing);
            xlApp.Quit();
            // 安全回收进程
            System.GC.GetGeneration(xlApp);
            IntPtr t = new IntPtr(xlApp.Hwnd);   //获取句柄
            int k = 0;
            GetWindowThreadProcessId(t, out k);   //获取进程唯一标志
            System.Diagnostics.Process p = System.Diagnostics.Process.GetProcessById(k);
            p.Kill();     //关闭进程
        }

2.使用NPOI

xlsx格式导出,可能有问题

using System.IO;
using NPOI;
using NPOI.SS.UserModel;

        private void btn_NPOI_Click(object sender, EventArgs e)
        {
            string importExcelPath = "E:\\import.xlsx";
            string exportExcelPath = "E:\\export.xlsx";
            IWorkbook workbook = WorkbookFactory.Create(importExcelPath);
            ISheet sheet = workbook.GetSheetAt(0);//获取第一个工作薄
            IRow row = (IRow)sheet.GetRow(0);//获取第一行

            //设置第一行第一列值,更多方法请参考源官方Demo
            row.CreateCell(0).SetCellValue("test");//设置第一行第一列值

            //导出excel
            FileStream fs = new FileStream(exportExcelPath, FileMode.Create, FileAccess.ReadWrite);
            workbook.Write(fs);
            fs.Close();
        }

3.使用ClosedXml

从Nuget下载 ClosedXml

using ClosedXML;
using ClosedXML.Excel;

        private void btn_ClosedXML_Click(object sender, EventArgs e)
        {
            string importExcelPath = "E:\\import.xlsx";
            string exportExcelPath = "E:\\export.xlsx";
            var workbook = new XLWorkbook(importExcelPath);

            IXLWorksheet sheet = workbook.Worksheet(1);//这个库也是从1开始
            //设置第一行第一列值,更多方法请参考官方Demo
            sheet.Cell(1, 1).Value = "test";//该方法也是从1开始，非0

            workbook.SaveAs(exportExcelPath);
        }

4.使用 spire.xls

spire分免费和收费，无特殊需求用免费即可

using Spire.Xls;

        private void btnSpire_Click(object sender, EventArgs e)
        {
            string importExcelPath = "E:\\import.xlsx";
            string exportExcelPath = "E:\\export.xlsx";

            Spire.Xls.Workbook workbook = new Spire.Xls.Workbook();
            workbook.LoadFromFile(importExcelPath);
            //处理Excel数据，更多请参考官方Demo
            Spire.Xls.Worksheet sheet = workbook.Worksheets[0];
            sheet.Range[1,1].Text = "test";//该方法也是从1开始，非0

            workbook.SaveToFile(exportExcelPath);
        }

参考 https://www.cnblogs.com/kenjiang/p/10790652.html

使用OLEDB

用OLEDB方式读取EXCEL的速度是非常快的。但是当Excel数据量很大时。会非常占用内存，当内存不够时会抛出内存溢出的异常。
OLEDB方式将Excel作为一个数据源，直接用Sql语句操作数据，并且不需要安装Office Excel就可以使用。但缺点是不能灵活操作Excel，例如设置字体，单元格格式等。

参考 https://blog.csdn.net/qq_33459369/article/details/79308361