apewer-dotnet/Apewer/Source/IndexAttribute.cs

using System;
using System.Collections.Generic;
using System.Reflection;

namespace Apewer.Source
{

    /// <summary>索引。</summary>
    [Serializable]
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]
    public sealed class IndexAttribute : Attribute, IToJson
    {

        PropertyInfo _property = null;
        ColumnAttribute _column;

        string _name = null;
        FieldOrder _order = FieldOrder.Ascend;

        /// <summary>索引名称。</summary>
        public string Name { get => _name; }

        /// <summary>排序。</summary>
        public FieldOrder Order { get => _order; set => _order = value; }

        /// <summary>列。</summary>
        public ColumnAttribute Column { get => _column; }

        /// <summary>属性。</summary>
        public PropertyInfo Property { get => _property; }

        /// <summary>表示此属性是索引的一部分。</summary>
        /// <param name="name">索引名称。</param>
        public IndexAttribute(string name)
        {
            if (string.IsNullOrEmpty(name)) throw new ArgumentNullException(nameof(name));
            _name = name;
        }

        internal void SetColumn(ColumnAttribute column)
        {
            _column = column;
        }

        /// <summary>解析列的索引。</summary>
        /// <remarks>注意：此方法不再抛出异常，当不存在正确的列特性时将返回 NULL 值</remarks>
        public static IndexAttribute[] Parse(PropertyInfo property)
        {
            if (property == null) return null;

            var attributes = property.GetCustomAttributes(typeof(IndexAttribute), true);
            var ias = new List<IndexAttribute>();
            foreach (var attribute in attributes)
            {
                var ia = attribute as IndexAttribute;
                if (ia == null) continue;
                if (ia._name.IsEmpty()) continue;

                ia._property = property;
                ias.Add(ia);
            }
            return ias.ToArray();
        }

        /// <summary>生成 Json 对象。</summary>
        /// <exception cref="NotImplementedException"></exception>
        public Json ToJson()
        {
            var json = Json.NewObject();
            json.SetProperty("name", _name);
            json.SetProperty("order", _order.ToString());
            if (_column != null) json.SetProperty("column", _column.ToJson());
            return json;
        }

        /// <summary></summary>
        public override string ToString() => $"Index = {_name}, Field = {_column?.Field}, Order = {_order}";

    }

}