ラムダ式で指定したプロパティの属性を取得するサンプル

GetAttributes.cs

    static class Program
    {
        static void Main(string[] args)
        {
            var test = new Test();
            Console.WriteLine(test.GetFugaString(x => x.TestProperty));
            Console.Read();
        }

        public static string GetFugaString<TSource, TSelector>(this TSource source, Expression<Func<TSource, TSelector>> propertyExpression) where TSource : class
        {
            var attrs = GetAttributes(propertyExpression);
            foreach(var item in attrs)
            {
                HogeAttribute attr;
                if(item is HogeAttribute)
                {
                    attr = item as HogeAttribute;

                    return attr.Fuga;
                }
            }
            return "";
        }

        private static object[] GetAttributes<TSource, TSelector>(Expression<Func<TSource, TSelector>> propertyExpression)
        {
            if(propertyExpression == null) throw new ArgumentNullException("propertyExpression");

            if(!(propertyExpression.Body is MemberExpression)) throw new NotSupportedException("このメソッドでは x => x.プロパティ の形式のラムダ式以外許可されません");

            var memberExpression = (MemberExpression)propertyExpression.Body;

            return memberExpression.Member.GetCustomAttributes(false);
        }
    }

    public class Test
    {
        [Hoge(Fuga = "ふが～")]
        public string TestProperty { get; set; }
    }

    public class HogeAttribute : Attribute
    {
        public string Fuga { get; set; }
    }