* 使用 Npoi

services.AddNpoiExcel();

* 使用 EpPlus

services.AddEpPlusExcel();

    //导入类
    public class ImportTest
    {
        [Display(Name = "姓名")]
        [Required(ErrorMessage = "{0}不能为空")]
        [StringLength(4, ErrorMessage = "{0}最大长度为{1}")]
        public virtual string Name { get; set; }

        [Display(Name = "手机号")]
        [RegularExpression(@"^1[3456789]\d{9}$", ErrorMessage = "{0}格式错误")]
        public virtual string Phone { get; set; }

        [Display(Name = "年龄")]
        [Required(ErrorMessage = "{0}不能为空")]
        [Range(10, 100, ErrorMessage = "{0}区间为{1}~{2}")]
        public virtual int Age { get; set; }

        [Display(Name = "成绩")]
        [Range(0, 150, ErrorMessage = "{0}区间为{1}~{2}")]
        public virtual decimal? Score { get; set; }

        [Display(Name = "日期")]
        [DefaultValue(typeof(DateTime), "2020-9-9")]
        public virtual DateTime Date { get; set; }

        [Display(Name = "学历")]
        [EnumDataType(typeof(TestEnum), ErrorMessage = "{0}值不存在")]
        public virtual TestEnum? Edu { get; set; }

        public virtual string NoDisplayName { get; set; }

        [IgnoreColumn]
        public virtual string IgnoreName { get; set; }
    }

    //导入方法
    public async Task Import(Stream stream)
    {
       try
        {
            var data = await _excelImportManager.ImportAsync<ImportTest>(stream, opt =>
            {
               // opt.SheetIndex = 0;
               // opt.ValidateMode = ExcelValidateModeEnum.ThrowRow;//可设置异常处理模式
            });

            //检查错误并抛出异常
            data.CheckError();

            //获取有效数据
            var valid = data.GetValidData();

            //获取无效数据
            var invalid = data.GetInvalidData();

            //获取全部数据
            var all = data.GetAllData();

            //获取错误信息，若无错误则返回null
            var error = data.GetErrorMessage();
        }
        catch (Exception e)
        { 
            //返回错误信息： e.Message
        }
    }

    //导出类
    [HeaderStyle(ColumnAutoSize = true)]
    [RowHeight(20, 30)]
    [HeaderFont(Color = 14)]
    [DataStyle(FillPattern = (short)FillPattern.SolidForeground, FillForegroundColor = HSSFColor.LightOrange.Index)]
    [DataFont(Color = 16)]
    [MergeColumn(nameof(Edu), nameof(Name11))]
    public class ExportTest
    {
        [Display(Name = "姓名")]
        [DataStyle(WrapText = true, FillPattern = (short)FillPattern.SolidForeground, FillForegroundColor = HSSFColor.Green.Index)]
        [DataFont(Color = 10)]
        [MergeRow]
        public virtual string Name { get; set; }

        [Display(Name = "生日")]
        [DataStyle(DataFormat = "yyyy\"年\"m\"月\"d\"日\";@")]
        [DefaultValue(typeof(DateTime), "2020-9-9")]
        public virtual DateTime? Date { get; set; }

        [Display(Name = "年龄")]
        [ColumnStats((int)FunctionEnum.Avg)]
        public virtual int Age { get; set; }

        [Display(Name = "成绩")]
        [HeaderFont(Color = 15)]
        [DataStyle(DataFormat = "#,##0.00_ ")]
        [ColumnStats((int)FunctionEnum.Avg, OffsetRow = 4)]
        [ColumnStats((int)FunctionEnum.Sum)]
        public virtual decimal? Score { get; set; }

        [Display(Name = "是否及格")]
        public virtual bool IsPass => Score > 3000;

        [Display(Name = "学历")]
        [IgnoreColumn]
        public virtual TestEnum? Edu { get; set; }

        [Display(Name = "学历文本")]
        public virtual string EduText => Edu?.ToString();

        [Display(Name = "时间")]
        public virtual TimeSpan Time =>TimeSpan.FromDays(1);
    }
    
    //导出方法
    public async Task<byte[]> Export(List<ExportTest> list)
    { 
        try
        {
           var bytes = await _excelExportManager.ExportAsync<ExportTest>(list, opt =>
            {
                //opt.ExcelType = ExcelTypeEnum.Xlsx;
                //opt.SheetName = "sheet名称";
            },new []{"姓名","生日"});

            return bytes;
        }
        catch (Exception e)
        { 
            //返回错误信息： e.Message
        }
    }

    // 获取excel文件
    public FileStreamResult GetExcel(byte[] buffer)
    {
        string xlsMime = "application/vnd.ms-excel";
        string xlsxMime = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        Stream stream = new MemoryStream(buffer);
        stream.Seek(0, SeekOrigin.Begin);

        return new FileStreamResult(stream, xlsxMime)
        {
            FileDownloadName = "导出的Excel.xlsx"
        };
    }