[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property)]
    public abstract class DecoratorAttributeBase : Attribute
    {
        public abstract void Intercept(object target);
    }

      /// <summary>
   /// 实际代理对象
   /// </summary>
    public class CustomProxy<T> : RealProxy, IDisposable where T : MarshalByRefObject
    {
        /// <summary>
        /// 构造过程中把Proxy需要操作的内容与实际目标对象实例Attach到一起
        /// </summary>
        /// <param name="target"></param>
        public CustomProxy(T target):base(target.GetType())
        {
            AttachServer(target);
        }#region IDisposable 成员
        /// <summary>
        /// 析构过程则借助Proxy和目标对象实例的Attach，便于GC回收
        /// </summary>
        public void Dispose()
        {
            DetachServer();
        }#endregion/// <summary>
        /// 创建目标实例的transparent代理对象
        /// </summary>
        /// <param name="target"></param>
        /// <returns></returns>
        public static T Create(T target)
        {
            if (target == null)
            {
                throw new ArgumentNullException("target");
            }return (T)(new CustomProxy<T>(target).GetTransparentProxy());
        }public override IMessage Invoke(IMessage msg)
        {
            MethodCallMessageWrapper caller = new MethodCallMessageWrapper((IMethodCallMessage)msg);//提取实际宿主对象
            MethodInfo method = (MethodInfo)caller.MethodBase;
            T target = (T)GetUnwrappedServer();
            DecoratorAttributeBase[] attributes = 
                (DecoratorAttributeBase[])method.GetCustomAttributes(typeof(DecoratorAttributeBase), true);if (attributes.Length > 0)
            {
                foreach (DecoratorAttributeBase attribute in attributes)
                {
                    attribute.Intercept(caller);
                }
            }object ret = method.Invoke(target,caller.Args);return new ReturnMessage(ret, caller.Args, caller.ArgCount, caller.LogicalCallContext, caller);
        }
    }

    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
    public class ArgumentNotEmptyAttribute : DecoratorAttributeBase
    {
        public override void Intercept(object target)
        {
            MethodCallMessageWrapper caller = new MethodCallMessageWrapper((IMethodCallMessage)target);if (caller.ArgCount == 0)
            {
                return;
            }foreach (object arg in caller.Args)
            {
                if ((string.IsNullOrEmpty((string)arg)))
                {
                    throw new ArgumentException("string is null or empty");
                }
            }
        }
    }
    [AttributeUsage(AttributeTargets.Method, AllowMultiple 
= false)]
    public class ArgumentTypeRestrictionAttribute : DecoratorAttributeBase
    {
        private Type type;
        public ArgumentTypeRestrictionAttribute(Type type)
        {
            this.type = type;
        }public override void Intercept(object target)
        {
            MethodCallMessageWrapper caller = new MethodCallMessageWrapper((IMethodCallMessage)target);if (caller.ArgCount == 0)
            {
                return;
            }for (int i = 0; i < caller.ArgCount; i++)
            {
                object arg = caller.Args[i];if ((arg.GetType() != this.type) && (!arg.GetType().IsAssignableFrom(this.type)))
                {
                    throw new ArgumentException(i.ToString());
                }
            }
        }
    }

    class User : MarshalByRefObject
    {
        private string name;
        private string title;
        [ArgumentTypeRestriction(
typeof(string))]   // 提供拦截入口
        [ArgumentNotEmpty()]                        // 提供拦截入口
        public void SetUserInfo(object name, object title)
        {
            this.name = (string)name;
            this.title = (string)title;
        }
    }

        [TestMethod]
        public void TestCSharpAOP()
        {
            User user = CustomProxy<User>.Create(new User());
            user.SetUserInfo(
"joe","manager");try 
            {
                user.SetUserInfo(20, "manager");
            }
            catch (Exception ex)
            {
                Assert.AreEqual<string>("0", ex.Message);
            }try
            {
                user.SetUserInfo("", "manager");
            }
            catch (Exception ex)
            {
                Assert.AreEqual<string>("string is null or empty", ex.Message);
            }
        }