Fork/Fork.Net/Y.Utils/AttributeUtils/CustomAttributeHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Y.Utils.AttributeUtils
{
    public static class CustomAttributeHelper
    {
        /// <summary>  
        /// Cache Data  
        /// </summary>  
        private static readonly Dictionary<string, string> Cache = new Dictionary<string, string>();

        /// <summary>  
        /// 获取CustomAttribute Value  
        /// </summary>  
        /// <typeparam name="T">Attribute的子类型</typeparam>  
        /// <param name="sourceType">头部标有CustomAttribute类的类型</param>  
        /// <param name="attributeValueAction">取Attribute具体哪个属性值的匿名函数</param>  
        /// <returns>返回Attribute的值，没有则返回null</returns>  
        public static string GetCustomAttributeValue<T>(this Type sourceType, Func<T, string> attributeValueAction) where T : Attribute
        {
            return GetAttributeValue(sourceType, attributeValueAction, null);
        }

        /// <summary>  
        /// 获取CustomAttribute Value  
        /// </summary>  
        /// <typeparam name="T">Attribute的子类型</typeparam>  
        /// <param name="sourceType">头部标有CustomAttribute类的类型</param>  
        /// <param name="attributeValueAction">取Attribute具体哪个属性值的匿名函数</param>  
        /// <param name="name">field name或property name</param>  
        /// <returns>返回Attribute的值，没有则返回null</returns>  
        public static string GetCustomAttributeValue<T>(this Type sourceType, Func<T, string> attributeValueAction,
            string name) where T : Attribute
        {
            return GetAttributeValue(sourceType, attributeValueAction, name);
        }

        private static string GetAttributeValue<T>(Type sourceType, Func<T, string> attributeValueAction,
            string name) where T : Attribute
        {
            var key = BuildKey(sourceType, name);
            if (!Cache.ContainsKey(key))
            {
                CacheAttributeValue(sourceType, attributeValueAction, name);
            }

            return Cache[key];
        }

        /// <summary>  
        /// 缓存Attribute Value  
        /// </summary>  
        private static void CacheAttributeValue<T>(Type type,
            Func<T, string> attributeValueAction, string name)
        {
            var key = BuildKey(type, name);

            var value = GetValue(type, attributeValueAction, name);

            lock (key + "_attributeValueLockKey")
            {
                if (!Cache.ContainsKey(key))
                {
                    Cache[key] = value;
                }
            }
        }

        private static string GetValue<T>(Type type,
            Func<T, string> attributeValueAction, string name)
        {
            object attribute = null;
            if (string.IsNullOrEmpty(name))
            {
                attribute =
                    type.GetCustomAttributes(typeof(T), false).FirstOrDefault();
            }
            else
            {
                var propertyInfo = type.GetProperty(name);
                if (propertyInfo != null)
                {
                    attribute =
                        propertyInfo.GetCustomAttributes(typeof(T), false).FirstOrDefault();
                }

                var fieldInfo = type.GetField(name);
                if (fieldInfo != null)
                {
                    attribute = fieldInfo.GetCustomAttributes(typeof(T), false).FirstOrDefault();
                }
            }

            return attribute == null ? null : attributeValueAction((T)attribute);
        }

        /// <summary>  
        /// 缓存Collection Name Key  
        /// </summary>  
        private static string BuildKey(Type type, string name)
        {
            if (string.IsNullOrEmpty(name))
            {
                return type.FullName;
            }

            return type.FullName + "." + name;
        }
    }
}