.NET 自带的动态代理+Expression 实现AOP

下面代码（摘抄之别处，原创在哪不知）是采用TransparentProxy和RealProxy实现对象的动态代理。碍于其使用反射掉用方法，所以就小试着将反射改成Expression以提高执行的效率。第15行就是原来代码中反射掉用方法的关键代码。

using System.Runtime.Remoting.Proxies;
using System.Runtime.Remoting.Messaging;
    //RealProxy
    public class MyRealProxy<T>:RealProxy
    {
        private T _target;
        public MyRealProxy(T target) : base(typeof(T))
        {
            this._target = target;
        }
       public override IMessage Invoke(IMessage msg)
       {
            PreProceede(msg);
            IMethodCallMessage callMessage = (IMethodCallMessage)msg;
            object returnValue = callMessage.MethodBase.Invoke(this._target, callMessage.Args);
            PostProceede(msg);
            return new ReturnMessage(returnValue, new object[0], 0, null, callMessage);
        }
       public void PreProceede(IMessage msg)
       {
           Console.WriteLine("方法执行前");
       }
       public void PostProceede(IMessage msg)
       {
           Console.WriteLine("方法执行后");
       }
    }
   //TransparentProxy
   public static class TransparentProxy
   {
        public static T Create<T>()
        {
           T instance = Activator.CreateInstance<T>();
           MyRealProxy<T> realProxy = new MyRealProxy<T>(instance);
           T transparentProxy = (T)realProxy.GetTransparentProxy();
           return transparentProxy;
        }
   }

其他的辅助类

    public class User 
    {
        public string Name { get; set; }
        public string PassWord { get; set; }
    }

    public interface IUserProcessor
    {
        void RegUser(User user);
    }

    public class UserProcessor : MarshalByRefObject, IUserProcessor
    {
        public void RegUser(User user)
        {
            Console.WriteLine("Already registered.");
        }

        public string RegUser2(User user)
        {
            Console.WriteLine("Already registered.");
            return "OK";
        }
    }

    public class RemotingProxy
    {
        public void Execute()
        {
            try
            {
                User user = new User() { Name = "HK", PassWord = "12345" };
                UserProcessor userprocessor = TransparentProxy.Create<UserProcessor>();
                userprocessor.RegUser(user);
                Console.WriteLine(userprocessor.RegUser2(user));
            }
            catch (Exception ex)
            {
                throw ex;
            }

        }
    }

将15行替换为如下Expression实现的代码。