Attribute.GetCustomAttribute() 返回为null

[叶落_下]

namespace LookUpWhatsNew
{
    internal class WhatsNewChecker
    {
        private static readonly StringBuilder outPutText = new StringBuilder();
        private static DateTime backDateTo = new DateTime(2010,2,1);

        static void Main(string[] args)
        {
            Assembly theAssembly = Assembly.Load("VectorClass");
            Attribute supportsAttibute = Attribute.GetCustomAttribute(theAssembly, typeof(LastModifiedAttribute));//  supportsAttibute 为空！      
            Conso.Read();
        }
   }
}

namespace WhatNewAttributes
{
    [AttributeUsage(AttributeTargets .Class |AttributeTargets.Method ,AllowMultiple =true ,Inherited =false )]
    public class LastModifiedAttribute:Attribute 
    {
        private readonly DateTime dateModified;
        private readonly string changes;
        public LastModifiedAttribute(string dateModified, string changes)
        {
            this.dateModified = DateTime.Parse(dateModified);
            this.changes = changes;
        }
        public DateTime DateModified
        {
            get
            {
                return this.dateModified;
            }
        }
        public string Changes
        {
            get
            {
                return this.changes;
            }
        }
        public string Issues { get; set; }
    }
    [AttributeUsage(AttributeTargets.Assembly)]
    public class SupportWhatsNewAttribute : Attribute
    {
    }
}

namespace VectorClass
{
    [LastModifiedAttribute("14,Feb,2010", "IEnumerable interface implemented so vector can now be treated as a Collection")]
    [LastModifiedAttribute("10,Feb,2010", "IFormattable interface implemented so vector now responds to format specifiers N and VE")]
    public class Vector:IEnumerable ,IFormattable
    {
        public double x, y, z;
        public Vector(double x,double y,double z)
        {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        [LastModifiedAttribute("10,Feb,2010", "Method added in order to formating support")]
        public string ToString(string format, IFormatProvider formatProvider)
        {
            if (format == null)
            {
                return ToString();
            }

            switch (format)
            {
                case "N":
                    return string.Format("({0},{1},{2})", x, y, z);
                case "VE":
                    return string.Format("{0}i+{1}j+{2}k", x, y, z);
                default:
                    throw new ArgumentException("No {0} format !", format);
            }
        }

        public string ToString(string format)
        {
            return ToString(format, null);
        }

        public IEnumerator GetEnumerator()
        {
            yield return x;
            yield return y;
            yield return z;
        }
        [LastModifiedAttribute("14,Feb,2010", "Class create as part of collection support for Vector")]
        private class VectorIEnumerator : IEnumerator
        {

            public object Current
            {
                get { throw new NotImplementedException(); }
            }

            public bool MoveNext()
            {
                throw new NotImplementedException();
            }

            public void Reset()
            {
                throw new NotImplementedException();
            }
        }
    }
}

[叶落_下]

大神请解释为何出现这种情况。谢谢！

[gomoku]

LastModifiedAttribute只能修饰到类和方法，而不能修饰到assembly。 因此，Attribute.GetCustomAttribute(Assembly, Type)不能得到任何东西。 要得到Vector类的LastModified，可以： Type vectorType = theAssembly.GetType("VectorClass.Vector"); Attribute modifiedAttibute = vectorType.GetCustomAttributes(false).OfType<LastModifiedAttribute>().FirstOrDefault(); 要得到assembly的attribute，可以： 1、目标assembly要有特性标志： [assembly:SupportWhatsNew] 2、获得assembly级别的特性： Attribute whatsNew = Attribute.GetCustomAttribute(theAssembly, typeof(SupportWhatsNewAttribute))