导出合并行及合并列

   [HttpGet]
        public async Task<ActionResult> DownTestFile(RedScarfBadgeManage.Dto.RedScarfBadgeStudentListByConditionInput input)
        {

           
                    using (var client = new WebClient())
                    {
                        byte[] bytes =await _RedScarfBadgeManageAppService.ExportRedScarfBadgeStudentListByConditionToExcel(input);

                        return File(bytes, "application/octet-stream", "ceshi.xlsx");
                    }
        }

  MemoryStream stream = new MemoryStream();
            ExcelPackage.LicenseContext = LicenseContext.NonCommercial;
            using (ExcelPackage package = new ExcelPackage(stream))
            {

                ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Test");
                worksheet.OutLineApplyStyle = true;
                //添加表头
                worksheet.Cells[1, 1].Value = "学校";
                worksheet.Cells[1, 1].Style.Font.Bold = true;
                worksheet.Cells[1, 2].Value = "年级";
                worksheet.Cells[1, 2].Style.Font.Bold = true;
                worksheet.Cells[1, 3].Value = "班级";
                worksheet.Cells[1, 3].Style.Font.Bold = true;
                worksheet.Cells[1, 4].Value = "登录账号";
                worksheet.Cells[1, 4].Style.Font.Bold = true;
                worksheet.Cells[1, 5].Value = "学生姓名";
                worksheet.Cells[1, 5].Style.Font.Bold = true;
                worksheet.Cells[1, 6].Value = "奖章总数";
                worksheet.Cells[1, 6].Style.Font.Bold = true;
                worksheet.Cells[2, 1].Value = "学校";
                worksheet.Cells[2, 1].Style.Font.Bold = true;
                worksheet.Cells[2, 2].Value = "年级";
                worksheet.Cells[2, 2].Style.Font.Bold = true;
                worksheet.Cells[2, 3].Value = "班级";
                worksheet.Cells[2, 3].Style.Font.Bold = true;
                worksheet.Cells[2, 4].Value = "登录账号";
                worksheet.Cells[2, 4].Style.Font.Bold = true;
                worksheet.Cells[2, 5].Value = "学生姓名";
                worksheet.Cells[2, 5].Style.Font.Bold = true;
                worksheet.Cells[2, 6].Value = "奖章总数";
                worksheet.Cells[2, 6].Style.Font.Bold = true;
                //合并列（开始行，开始列，结束行，结束列）
                MergeColCells(worksheet, 1, 1, 2, 1);
                MergeColCells(worksheet, 1, 2, 2, 2);
                MergeColCells(worksheet, 1, 3, 2, 3);
                MergeColCells(worksheet, 1, 4, 2, 4);
                MergeColCells(worksheet, 1, 5, 2, 5);
                MergeColCells(worksheet, 1, 6, 2, 6);
                var i = 7;
                var j = 0;
                foreach (var m in cList)
                {
                    j = i;
                    foreach (var n in m.BadgeChildDto)
                    {
                        worksheet.Cells[1, i].Value = m.ChapterTypeName;
                        worksheet.Cells[1, i].Style.Font.Bold = true;
                        worksheet.Cells[2, i].Value = n.BadgeName;
                        worksheet.Cells[2, i].Style.Font.Bold = true;
                        i++;

                    }
                    MergeColCells(worksheet, 1, j, 1, i-1);

                }
           
                package.Save();
            }

            return stream.GetBuffer();

 /// <summary>
        /// 合并单元格
        /// </summary>
        /// <param name="sheet"></param>
        public static void MergeColCells(ExcelWorksheet sheet, int fromRow, int fromCol,int toRow,int toCol)
        {

            sheet.Cells[fromRow,fromCol,toRow,toCol].Merge = true;
            sheet.Cells[fromRow, fromCol, toRow, toCol].Style.VerticalAlignment = OfficeOpenXml.Style.ExcelVerticalAlignment.Center;
            sheet.Cells[fromRow, fromCol, toRow, toCol].Style.HorizontalAlignment = OfficeOpenXml.Style.ExcelHorizontalAlignment.Center;

        }

引用：https://www.cnblogs.com/jishugaochao/p/10344912.html