CustomAttributeHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;

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;
    }
}