.net 动态代理实现

1、先新建一个要被代理的类，必须实现  MarshalByRefObject

public class User: MarshalByRefObject
    {
        public string SayHello()
        {
            Console.WriteLine("I am SayHello");
            return "I am SuperMan";
        }
    }

2、创建类 用于代理类执行方法 

 /// 
    /// 动态代理要执行的方法
    /// 
    public class DynamicAction
    {
        /// 
        /// 执行目标方法前执行
        /// 
        public Action BeforeAction { get; set; }
        /// 
        /// 执行目标方法后执行
        /// 
        public Action AfterAction { get; set; }
    }

3、创建代理类  必须继承 RealProxy类

public class DynamicProxy<T> : RealProxy
    {
        private readonly T _targetInstance = default(T);
 
        public Dictionary<string, DynamicAction> ProxyMethods { get; set; }
        public DynamicProxy(T targetInstance) : base(typeof(T))
        {
            _targetInstance = targetInstance;
        }
        public override IMessage Invoke(IMessage msg)
        {
            var reqMsg = msg as IMethodCallMessage;
 
            if (reqMsg == null)
            {
                return new ReturnMessage(new Exception("调用失败！"), null);
            }
 
            var target = _targetInstance as MarshalByRefObject;
 
            if (target == null)
            {
                return new ReturnMessage(new Exception("调用失败！请把目标对象 继承自 System.MarshalByRefObject"), reqMsg);
            }
 
            var methodName = reqMsg.MethodName;
 
            DynamicAction actions = null;
 
            if (ProxyMethods != null && ProxyMethods.ContainsKey(methodName))
            {
                actions = ProxyMethods[methodName];
            }
 
            if (actions != null && actions.BeforeAction != null)
            {
                actions.BeforeAction();
            }
 
            IMethodCallMessage callMessage = (IMethodCallMessage)msg;
            var result = RemotingServices.ExecuteMessage(target, reqMsg);
 
            if (actions != null && actions.AfterAction != null)
            {
                actions.AfterAction();
            }
 
            return result;
        }
    }

4、创建代理工厂类

/// 
    /// 代理工厂
    /// 
    /// 
    public class ProxyFactory<T>
    {
        public static T Create(T obj, Dictionary<string, DynamicAction> proxyMethods = null)
        {
            var proxy = new DynamicProxy(obj) { ProxyMethods = proxyMethods };
 
            return (T)proxy.GetTransparentProxy();
        }
    }

5、测试

class Program
    {
        static void Main(string[] args)
        {
            var proxyMotheds = new Dictionary<string, DynamicAction>();
            proxyMotheds.Add("SayHello", new DynamicAction()
            {
                BeforeAction = new Action(() => Console.WriteLine("Before Doing....")),
                AfterAction = new Action(() => Console.WriteLine("After Doing...."))
            });
 
            var user = new User();
            var t = ProxyFactory.Create(user, proxyMotheds);
            t.SayHello();
        }
    }