/MVC.Controls/AttributeHelper.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Linq.Expressions;

using System.Reflection;

using System.ComponentModel.DataAnnotations;



namespace MVC.Controls

{

    public static class AttributeHelper

    {

        private static Dictionary<object, List<Attribute>> _attributeCache = new Dictionary<object, List<Attribute>>();



        public static Dictionary<object, List<Attribute>> AttributeCache { get { return _attributeCache; } }



        // Types

        public static List<Attribute> GetTypeAttributes<TType>()

        {

            return GetTypeAttributes(typeof(TType));

        }



        public static List<Attribute> GetTypeAttributes(Type type)

        {

            return LockAndGetAttributes(type, tp => ((Type)tp).GetCustomAttributes(true));

        }



        public static List<TAttributeType> GetTypeAttributes<TAttributeType>(Type type, Func<TAttributeType, bool> predicate = null)

        {

            return

                GetTypeAttributes(type)

                    .OfType<TAttributeType>()

                    .Where(attr => predicate == null || predicate(attr))

                    .ToList();

        }



        public static List<TAttributeType> GetTypeAttributes<TType, TAttributeType>(Func<TAttributeType, bool> predicate = null)

        {

            return GetTypeAttributes(typeof(TType), predicate);

        }



        public static TAttributeType GetTypeAttribute<TType, TAttributeType>(Func<TAttributeType, bool> predicate = null)

        {

            return

                GetTypeAttribute(typeof(TType), predicate);

        }



        public static TAttributeType GetTypeAttribute<TAttributeType>(Type type, Func<TAttributeType, bool> predicate = null)

        {

            return

                GetTypeAttributes<TAttributeType>(type, predicate)

                    .FirstOrDefault();

        }



        public static bool HasTypeAttribute<TType, TAttributeType>(Func<TAttributeType, bool> predicate = null)

        {

            return HasTypeAttribute<TAttributeType>(typeof(TType), predicate);

        }



        public static bool HasTypeAttribute<TAttributeType>(Type type, Func<TAttributeType, bool> predicate = null)

        {

            return GetTypeAttribute<TAttributeType>(type, predicate) != null;

        }



        // Members and properties

        public static List<Attribute> GetMemberAttributes<TType>(Expression<Func<TType, object>> action)

        {

            return GetMemberAttributes(GetMember(action));

        }



        public static List<TAttributeType> GetMemberAttributes<TType, TAttributeType>(

            Expression<Func<TType, object>> action,

            Func<TAttributeType, bool> predicate = null)

            where TAttributeType : Attribute

        {

            return GetMemberAttributes<TAttributeType>(GetMember(action), predicate);

        }



        public static TAttributeType GetMemberAttribute<TType, TAttributeType>(

            Expression<Func<TType, object>> action,

            Func<TAttributeType, bool> predicate = null)

            where TAttributeType : Attribute

        {

            return GetMemberAttribute<TAttributeType>(GetMember(action), predicate);

        }



        public static bool HasMemberAttribute<TType, TAttributeType>(Expression<Func<TType, object>> action, Func<TAttributeType, bool> predicate = null) where TAttributeType : Attribute

        {

            return GetMemberAttribute(GetMember(action), predicate) != null;

        }



        // MemberInfo (and PropertyInfo since PropertyInfo inherits from MemberInfo)

        public static List<Attribute> GetMemberAttributes(this MemberInfo memberInfo)

        {

            return

                LockAndGetAttributes(memberInfo, mi => GetMemberAttributesWithMeta((MemberInfo)mi).ToArray());

        }



        public static List<Attribute> GetMemberAttributesWithMeta(this MemberInfo mi) 

        {

            List<Attribute> result =

                mi

                    .GetCustomAttributes(true)

                    .OfType<Attribute>()

                    .ToList();



            foreach(MetadataTypeAttribute meta in GetTypeAttributes<MetadataTypeAttribute>(mi.DeclaringType))

            {

                MemberInfo[] metaMembers = meta.MetadataClassType.GetMember(mi.Name);

                foreach(MemberInfo mi2 in metaMembers)

                {

                    result.AddRange(mi2.GetCustomAttributes(true).OfType<Attribute>());

                }

            }

            return result;

        }



        public static List<TAttributeType> GetMemberAttributes<TAttributeType>(this MemberInfo memberInfo, Func<TAttributeType, bool> predicate = null) where TAttributeType : Attribute

        {

            return

                GetMemberAttributes(memberInfo)

                    .OfType<TAttributeType>()

                    .Where(attr => predicate == null || predicate(attr))

                    .ToList();

        }



        public static TAttributeType GetMemberAttribute<TAttributeType>(this MemberInfo memberInfo, Func<TAttributeType, bool> predicate = null) where TAttributeType : Attribute

        {

            return

                GetMemberAttributes<TAttributeType>(memberInfo, predicate)

                    .FirstOrDefault();

        }



        public static bool HasMemberAttribute<TAttributeType>(this MemberInfo memberInfo, Func<TAttributeType, bool> predicate = null) where TAttributeType : Attribute

        {

            return

                memberInfo.GetMemberAttribute<TAttributeType>(predicate) != null;

        }



        // Internal stuff

        private static TType FirstOrDefault<TX, TType>(this IEnumerable<TX> list)

        {

            return

                list

                    .OfType<TType>()

                    .FirstOrDefault();

        }



        private static List<Attribute> LockAndGetAttributes(object key, Func<object, object[]> retrieveValue)

        {

            return

                LockAndGet<object, List<Attribute>>(_attributeCache, key, mi => retrieveValue(mi).Cast<Attribute>().ToList());

        }



        // Method for thread safely executing slow method and storing the result in a dictionary

        private static TValue LockAndGet<TKey, TValue>(Dictionary<TKey, TValue> dictionary, TKey key, Func<TKey, TValue> retrieveValue)

        {

            TValue value = default(TValue);

            lock (dictionary)

            {

                if (dictionary.TryGetValue(key, out value))

                {

                    return value;

                }

            }



            value = retrieveValue(key);



            lock (dictionary)

            {

                if (dictionary.ContainsKey(key) == false)

                {

                    dictionary.Add(key, value);

                }



                return value;

            }

        }



        public static MemberInfo GetMember<T>(Expression<Func<T, object>> expression)

        {

            MemberExpression memberExpression = expression.Body as MemberExpression;



            if (memberExpression != null)

            {

                return memberExpression.Member;

            }



            UnaryExpression unaryExpression = expression.Body as UnaryExpression;



            if (unaryExpression != null)

            {

                memberExpression = unaryExpression.Operand as MemberExpression;



                if (memberExpression != null)

                {

                    return memberExpression.Member;

                }



                MethodCallExpression methodCall = unaryExpression.Operand as MethodCallExpression;

                if (methodCall != null)

                {

                    return methodCall.Method;

                }

            }



            return null;

        }



        public static bool IsMember<T>(Expression<Func<T, object>> expression)

        {

            return GetMember<T>(expression) != null;

        }



        public static string GetMemberName<T>(T example, Expression<Func<T, object>> expression) where T : class

        {

            MemberExpression memberExpression = GetMemberExpression(expression);



            if (memberExpression == null)

            {

                return null;

            }



            if (memberExpression.Expression.NodeType == ExpressionType.MemberAccess)

            {

                MemberExpression innerMemberExpression = (MemberExpression)memberExpression.Expression;



                return memberExpression.ToString().Substring(innerMemberExpression.Expression.ToString().Length + 1);

            }



            return memberExpression.Member.Name;

        }



        public static string GetMemberName<T>(Expression<Func<T, object>> expression) where T : class

        {

            MemberExpression memberExpression = GetMemberExpression(expression);



            if (memberExpression == null)

            {

                return null;

            }



            if (memberExpression.Expression.NodeType == ExpressionType.MemberAccess)

            {

                MemberExpression innerMemberExpression = (MemberExpression)memberExpression.Expression;



                return memberExpression.ToString().Substring(innerMemberExpression.Expression.ToString().Length + 1);

            }



            return memberExpression.Member.Name;

        }



        public static MemberExpression GetMemberExpression<T>(Expression<Func<T, object>> expression) where T : class

        {

            MemberExpression memberExpression = expression.Body as MemberExpression;



            if (memberExpression == null)

            {

                UnaryExpression unaryExpression = expression.Body as UnaryExpression;



                if (unaryExpression != null)

                {

                    memberExpression = unaryExpression.Operand as MemberExpression;

                }

            }



            return memberExpression;

        }

    }

}