public class XXXXController : CoreController
{
    // 控制器內部
    
    [HttpPost]
    public ActionResult export()
    {
        // 控制器接口
        var list = op
                    .GetPagedQuery(PageModel)
                    .Select(s => new DesWeeklyReportExcExp
                    {
                        col1 = s.Project.ProjName,
                        col2 = s.ColAttROPDate1?.ToString("yyyy.MM.dd"),
                        col3 = (s.ColAttROPDate2 == null ? "無" : s.ColAttROPDate2.Value.ToString("yyyy.MM.dd"))
                                                       + "/"
                                                       + (s.ColAttROPDate3 == null ? "無" : s.ColAttROPDate3.Value.ToString("yyyy.MM.dd")),
                        col4 = s.ColAttROPDate4?.ToString("yyyy.MM.dd")
                    }).ToList();
         string filePath = Server.MapPath("~/download/[這是模板名稱].xlsx");
         string filename = Path.GetFileNameWithoutExtension(filePath);// 文件名稱
         string extension = Path.GetExtension(filePath);// 后綴名 帶點(.)
         string fileDownloadName = filename + extension;

         var fs = ExcelHelper.ExportToExcel(list, filePath).ToArray();
         return File(fs, "application/ms-excel", fileDownloadName);
    }
}

[ExcelExpClassAttribute(2, 0, 2, 0)]
public class DesWeeklyReportExcExp : ExcelSuper
{
    /// <summary>
    /// 列1
    /// </summary>
    [ExcelExp(SortIndex = 0, ColName = "列1")]
    public string col1 { get; set; }

    /// <summary>
    /// 列2
    /// </summary>
    [ExcelExp(SortIndex = 0, ColName = "列2")]
    public string col2 { get; set; }

    /// <summary>
    /// 列3
    /// </summary>
    [ExcelExp(SortIndex = 0, ColName = "列3")]
    public string col3 { get; set; }

    /// <summary>
    /// 列4
    /// </summary>
    [ExcelExp(SortIndex = 0, ColName = "列4")]
    public string col4 { get; set; }
}