public interface IStorageNode
    {
        bool IsDead { get; set; }
        void Save(string message);
    }
    public interface IDao { }
    public class BaseNode : IDao
    {
        protected string TestBase()
        {
            return "BaseNode";
        }
    }
    public class StorageNode : BaseNode, IStorageNode
    {
        private string _name;
        public StorageNode(string name)
        {
            this._name = name;
        }
        public bool IsDead { get; set; }
        public void Save(string message)
        {
            Console.WriteLine(string.Format("\"{0}\" was saved to {1}", message, this._name));
        }
    }
    public class DualNodeInterceptor : IInterceptor
    {
        private IStorageNode _slave;
        public DualNodeInterceptor(IStorageNode slave)
        {
            this._slave = slave;
        }
        public void Intercept(IInvocation invocation)
        {
            IStorageNode master = invocation.InvocationTarget as IStorageNode;
            if (master.IsDead)
            {
                IChangeProxyTarget cpt = invocation as IChangeProxyTarget;
                //将被代理对象master更换为slave
                cpt.ChangeProxyTarget(this._slave);
                //测试中恢复master的状态，以便看到随后的调用仍然使用master这一效果
                master.IsDead = false;
            }
            invocation.Proceed();
        }
    }
    public class CallingLogInterceptor : IInterceptor
    {
        private int _indent = 0;
        private void PreProceed(IInvocation invocation)
        {
            if (this._indent > 0)
                Console.Write(" ".PadRight(this._indent * 4, ' '));
            this._indent++;
            Console.Write("Intercepting: " + invocation.Method.Name + "(");
            if (invocation.Arguments != null && invocation.Arguments.Length > 0)
                for (int i = 0; i < invocation.Arguments.Length; i++)
                {
                    if (i != 0) Console.Write(", ");
                    Console.Write(invocation.Arguments[i] == null
                        ? "null"
                        : invocation.Arguments[i].GetType() == typeof(string)
                           ? "\"" + invocation.Arguments[i].ToString() + "\""
                           : invocation.Arguments[i].ToString());
                }
            Console.WriteLine(")");
        }
        private void PostProceed(IInvocation invocation)
        {
            this._indent--;
        }
        public void Intercept(IInvocation invocation)
        {
            this.PreProceed(invocation);
            invocation.Proceed();
            this.PostProceed(invocation);
        }
    }

  [TestMethod]
        public void TestMethod1()
        {
            ProxyGenerator generator = new ProxyGenerator();
            IDao daoInstance =new StorageNode("master");
            IStorageNode temp = daoInstance as IStorageNode;//为什么temp不为null
            IDao node1 = generator.CreateInterfaceProxyWithTarget(
                daoInstance
                , new DualNodeInterceptor(new StorageNode("slave"))
                , new CallingLogInterceptor());
            IStorageNode node = node1 as IStorageNode;//为什么node会是null
            node.Save("my message"); //应该调用master对象
            node.IsDead = true;
            node.Save("my message"); //应该调用slave对象
            node.Save("my message"); //应该调用master对象
        }