用Free Spire.XLS,可以从NuGet安装,也可以从这里下载安装然后手动引用DLL
Workbook workbook = new Workbook();
workbook.LoadFromFile("test.xlsx");
Worksheet sheet1 = workbook.Worksheets[0];
string value = sheet1.Range["A1"].Value;
Worksheet sheet2 = workbook.Worksheets[1];
sheet2.Range["A1"].Value = value;
workbook.SaveToFile("Result.xlsx", ExcelVersion.Version2013);