基於DotNetCoreNPOI封裝特性通用匯出excel

目前根據專案中的要求，支援列名定義，列索引排序，行合併單元格，EXCEL單元格的格式也是隨著資料的型別做對應的調整。

效果圖：

呼叫方式

可以看到時非常容易的能夠匯出資料，實際呼叫可能就三四句話

            // 你的需要匯出的資料集合，這裡的DownloadResponse就是你自己的資料集合
            List<DownloadResponse> dataList = GetDownloadList(data);
 
            // 匯出邏輯
            var workbook = new XSSFWorkbook();
            var sheet = workbook.CreateSheet("Sheet1");
            sheet.SetValue(PropertyHelper.GetPropertyGetters(dataList), workbook);
 
            string path = Path.Combine(@"D:\", $"{Guid.NewGuid()}.xlsx");
            // 輸出 Exce 檔案
            using (var fs = new FileStream(path, FileMode.Create, FileAccess.Write))
            {
                workbook.Write(fs);
            }

 public class DownloadResponse
    {
        /// <summary>
        /// 第一個引數：列名
        /// 第二個引數：索引(順序)
        /// 第三個引數：是否合併單元格
        /// 後期可以新增一些樣式，比如寬度，顏色等，暫時先這樣吧
        /// </summary>
        [Excel("Customs Area", 0, true)]
        public string? CustomsArea { get; set; }
        [Excel("Vender", 1, true)]
        public string? VendorCode { get; set; }
    }

實現程式碼

   public static class PropertyHelper
    {
        /// <summary>
        /// 獲取RemarkAttribute的值,並按index正序排序。
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dataList"></param>
        /// <returns></returns>
        public static Dictionary<int, List<PropertyGetterInfo>> GetPropertyGetters<T>(List<T> dataList)
        {
            var propertyGetters = GetExcelPropertyGetters<T>();

            var values = new Dictionary<int, List<PropertyGetterInfo>>();

            int rowIndex = 0;
            foreach (var response in dataList)
            {
                foreach (var getter in propertyGetters)
                {
                    string propertyName = getter.Key;
                    var attr = getter.Value.Attribute;

                    if (attr != null)
                    {
                        var value = getter.Value.Getter(response) as PropertyGetterInfo;
                        if (!values.TryGetValue(rowIndex, out var list))
                        {
                            list = new List<PropertyGetterInfo>();
                        }
                        list.Add(value);
                        values[rowIndex] = list;
                    }
                }
                rowIndex++;
            }
            return values;
        }

        /// <summary>
        /// 獲取ExcelAttribute的值。
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static Dictionary<string, PropertyGetterInfo<T>> GetExcelPropertyGetters<T>()
        {
            var result = new Dictionary<string, PropertyGetterInfo<T>>();
            var properties = (from property in typeof(T).GetProperties()
                                  //where Attribute.IsDefined(property, typeof(RemarkAttribute))
                              orderby ((ExcelAttribute)property
                                        .GetCustomAttributes(typeof(ExcelAttribute), false)
                                        .Single()).Index
                              select property).ToArray();
            foreach (var prop in properties)
            {
                var attr = prop.GetCustomAttribute<ExcelAttribute>();
                if (attr != null)
                {
                    var getter = CreateGetter<T>(prop);
                    result[prop.Name] = new PropertyGetterInfo<T>
                    {
                        Attribute = attr,
                        Getter = getter
                    };
                }
            }
            return result;
        }
        private static Func<T, PropertyGetterInfo> CreateGetter<T>(PropertyInfo prop)
        {
            var instance = Expression.Parameter(typeof(T), "instance");
            var propertyAccess = Expression.Property(instance, prop);
            var castToObject = Expression.Convert(propertyAccess, typeof(object));
            var lambdaBody = Expression.MemberInit(
                Expression.New(typeof(PropertyGetterInfo)),
                Expression.Bind(
                    typeof(PropertyGetterInfo).GetProperty(nameof(PropertyGetterInfo.Description)),
                    Expression.Constant(prop.GetCustomAttribute<ExcelAttribute>()?.Description ?? string.Empty)
                ),
                Expression.Bind(
                    typeof(PropertyGetterInfo).GetProperty(nameof(PropertyGetterInfo.Index)),
                    Expression.Constant(prop.GetCustomAttribute<ExcelAttribute>()?.Index ?? 0)
                ),
                Expression.Bind(
                    typeof(PropertyGetterInfo).GetProperty(nameof(PropertyGetterInfo.IsMerge)),
                    Expression.Constant(prop.GetCustomAttribute<ExcelAttribute>()?.IsMerge ?? false)
                ),
                Expression.Bind(
                    typeof(PropertyGetterInfo).GetProperty(nameof(PropertyGetterInfo.Value)),
                    Expression.TypeAs(castToObject, typeof(object))
                ),
                Expression.Bind(
                    typeof(PropertyGetterInfo).GetProperty(nameof(PropertyGetterInfo.ValueType)),
                    Expression.Constant(prop.PropertyType.FullName)
                )
            );
            var lambda = Expression.Lambda<Func<T, PropertyGetterInfo>>(lambdaBody, instance);
            return lambda.Compile();
        }
    }

    public class PropertyGetterInfo
    {
        public string Description { get; set; }
        public int Index { get; set; }
        public bool IsMerge { get; set; }
        public object? Value { get; set; }
        public string ValueType { get; set; }
    }
    public class PropertyGetterInfo<T>
    {
        public ExcelAttribute? Attribute { get; set; }
        public Func<T, object?> Getter { get; set; }
    }

     public class ExcelAttribute : Attribute
    {
        /// <summary>
        /// 列描述
        /// </summary>
        private string _description;
        /// <summary>
        /// 列索引
        /// </summary>
        private int _index;
        /// <summary>
        /// 是否合併
        /// </summary>
        private bool _isMerge;
        public ExcelAttribute(string desc)
        {
            _description = desc;
        }
        public ExcelAttribute(string desc, int index)
        {
            _description = desc;
            _index = index;
        }
        public ExcelAttribute(string desc, int index, bool isMerge)
        {
            _description = desc;
            _index = index;
            _isMerge = isMerge;
        }
        public string Description
        {
            get
            {
                return _description;
            }
        }
        public int Index
        {
            get
            {
                return _index;
            }
        }
        public bool IsMerge
        {
            get
            {
                return _isMerge;
            }
        }
    }

  public static class ExcelHelper
    {
        static readonly string? _intType = typeof(int).FullName;
        static readonly string? _intNullType = typeof(int?).FullName;
        static readonly string? _longType = typeof(long).FullName;
        static readonly string? _longNullType = typeof(long?).FullName;
        static readonly string? _doubleType = typeof(double).FullName;
        static readonly string? _doubleNullType = typeof(double?).FullName;
        static readonly string? _decimalType = typeof(decimal).FullName;
        static readonly string? _decimalNullType = typeof(decimal?).FullName;
        static readonly string? _stringType = typeof(string).FullName;
        static readonly string? _dateTimeType = typeof(DateTime).FullName;
        static readonly string? _dateTimeNullType = typeof(DateTime?).FullName;
        static readonly string? _boolType = typeof(bool).FullName;
        static readonly string? _boolNullType = typeof(bool?).FullName;
        static readonly string? _guidType = typeof(Guid).FullName;
        static readonly string? _guidNullType = typeof(Guid?).FullName;

        public static void SetValue(this ISheet sheet, Dictionary<int, List<PropertyGetterInfo>> propertyGetters, XSSFWorkbook workbook)
        {
            bool isHead = true;
            int sheetRowIndex = 0;
            for (int i = 0; i < propertyGetters.Count; i++)
            {
                var item = propertyGetters[i];
                // 建立表頭
                if (isHead)
                {
                    var headerRow = sheet.CreateRow(sheetRowIndex);
                    for (int j = 0; j < item.Count; j++)
                    {
                        headerRow.CreateCell(j).SetCellValue(item[j].Description);
                    }
                    isHead = false;
                    i--;
                    continue;
                }
                // 建立行
                sheetRowIndex++;
                var row = sheet.CreateRow(sheetRowIndex);
                for (int k = 0; k < item.Count; k++)
                {
                    var thisValue = item[k];
                    var cell = row.CreateCell(thisValue.Index);

                    if (thisValue.Value == null)
                    {
                        cell.SetCellType(CellType.String);
                        cell.SetCellValue(string.Empty);
                    }
                    if (thisValue.Value != null && thisValue.ValueType == _stringType)
                    {
                        cell.SetCellType(CellType.String);
                        cell.SetCellValue(thisValue.Value?.ToString());
                    }
                    // 數值型別
                    else if (thisValue.Value != null && (thisValue.ValueType == _intNullType
                       || thisValue.ValueType == _intType
                       || thisValue.ValueType == _decimalNullType
                       || thisValue.ValueType == _decimalType
                       || thisValue.ValueType == _longNullType
                       || thisValue.ValueType == _longType
                       || thisValue.ValueType == _doubleType
                       || thisValue.ValueType == _doubleNullType
                       ))
                    {
                        cell.SetCellType(CellType.Numeric);
                        double.TryParse(thisValue.Value?.ToString(), out double value);
                        cell.SetCellValue(value);
                    }
                    // 時間型別
                    else if (thisValue.Value != null && (thisValue.ValueType == _dateTimeNullType
                        || thisValue.ValueType == _dateTimeType))
                    {
                        DateTime.TryParse(thisValue.Value?.ToString(), out var value);
                        // 時間型別比較特殊，需要設定特定的單元格樣式
                        var style = workbook.CreateCellStyle();
                        cell.SetCellValue(value.ToOADate());
                        style = workbook.CreateCellStyle();
                        style.DataFormat = HSSFDataFormat.GetBuiltinFormat("m/d/yy");
                        cell.CellStyle = style;
                    }
                    // bool型別
                    else if (thisValue.Value != null && (thisValue.ValueType == _boolNullType
                        || thisValue.ValueType == _boolType))
                    {
                        cell.SetCellType(CellType.Boolean);
                        bool.TryParse(thisValue.Value?.ToString(), out bool value);
                        cell.SetCellValue(value);
                    }
                    // 合併單元格
                    if (thisValue.IsMerge && thisValue.Value != null)
                    {
                        int nextIndex = i + 1;
                        if (nextIndex >= propertyGetters.Count)
                        {
                            continue;
                        }
                        var nextValue = propertyGetters[nextIndex];
                        var e = nextValue.FirstOrDefault(x => x.Description == thisValue.Description && (x.Value?.Equals(thisValue.Value) ?? false));
                        if (e != null)
                        {
                            // 合併當前行和下一行
                            var range = new CellRangeAddress(sheetRowIndex, sheetRowIndex + 1, e.Index, e.Index);
                            sheet.AddMergedRegion(range);
                        }
                    }
                }
            }
        }

    }