class Program
{
 static void Main(string[] args)
 {
  //创建代理类，并把SampleProxy作为拦截器注入
  var sampleProxy = (targetInterface)SampleProxy.Create<targetInterface, SampleProxy>();
  //执行接口方法
  sampleProxy.Write("here is invoke by proxy");
 }
}

//需要被生成代理实例的接口
public interface targetInterface
{
 //这个方法会被代理类实现
 void Write(string writesomeshing);
}

public class SampleProxy : DispatchProxy
{
 /// <summary>
 /// 拦截调用
 /// </summary>
 /// <param name="method">所拦截的方法信息</param>
 /// <param name="parameters">所拦截方法被传入的参数指</param>
 /// <returns></returns>
 protected override object Invoke(MethodInfo targetMethod, object[] args)
 {
  Console.WriteLine(args[0]);
  return null;
 }
}

/// <summary>
/// 拦截器接口
/// </summary>
public interface IInterceptor
{
 /// <summary>
 /// 拦截器调用
 /// </summary>
 /// <param name="target">代理实例</param>
 /// <param name="method">所拦截的方法</param>
 /// <param name="parameters">所拦截方法传入的参数值</param>
 /// <returns>返回值会传递给方法返回值</returns> 
 object Intercept(object target, MethodInfo method, object[] parameters);
}

public class ProxyGenerator : DispatchProxy
{
 private IInterceptor interceptor { get; set; }

 /// <summary>
 /// 创建代理实例
 /// </summary>
 /// <param name="targetType">所要代理的接口类型</param>
 /// <param name="interceptor">拦截器</param>
 /// <returns>代理实例</returns>
 public static object Create(Type targetType, IInterceptor interceptor)
 {
  object proxy = GetProxy(targetType);
  ((ProxyGenerator)proxy).CreateInstance(interceptor);
  return proxy;
 }

 /// <summary>
 /// 创建代理实例
 /// </summary>
 /// <param name="targetType">所要代理的接口类型</param>
 /// <param name="interceptorType">拦截器类型</param>
 /// <param name="parameters">拦截器构造函数参数值</param>
 /// <returns>代理实例</returns>
 public static object Create(Type targetType, Type interceptorType, params object[] parameters)
 {
  object proxy = GetProxy(targetType);
  ((ProxyGenerator)proxy).CreateInstance(interceptorType, parameters);
  return proxy;
 }


 /// <summary>
 /// 创建代理实例 TTarget:所要代理的接口类型 TInterceptor:拦截器类型
 /// </summary>
 /// <param name="parameters">拦截器构造函数参数值</param>
 /// <returns>代理实例</returns>
 public static TTarget Create<TTarget, TInterceptor>(params object[] parameters) where TInterceptor : IInterceptor
 {
  var proxy = GetProxy(typeof(TTarget));
  ((ProxyGenerator)proxy).CreateInstance(typeof(TInterceptor), parameters);
  return (TTarget)proxy;
 }

 private static object GetProxy(Type targetType)
 {
  var callexp = Expression.Call(typeof(DispatchProxy), nameof(DispatchProxy.Create), new[] { targetType, typeof(ProxyGenerator) });
  return Expression.Lambda<Func<object(callexp).Compile()();
 }

 private void CreateInstance(Type interceptorType, object[] parameters)
 {
  var ctorParams = parameters.Select(x => x.GetType()).ToArray();
  var paramsExp = parameters.Select(x => Expression.Constant(x));
  var newExp = Expression.New(interceptorType.GetConstructor(ctorParams), paramsExp);
  this.interceptor = Expression.Lambda<Func<IInterceptor(newExp).Compile()();
 }

 private void CreateInstance(IInterceptor interceptor)
 {
  this.interceptor = interceptor;
 }

 protected override object Invoke(MethodInfo method, object[] parameters)
 {
  return this.interceptor.Intercept(method, parameters);
 }
}

 class Program
 {
  static void Main(string[] args)
  {
   var poxy1 = (targetInterface)ProxyGenerator.Create(typeof(targetInterface), new SampleProxy("coreproxy1"));
   poxy1.Write("here was invoked"); //---> "here was invoked by coreproxy1"

   var poxy2 = (targetInterface)ProxyGenerator.Create(typeof(targetInterface), typeof(SampleProxy), "coreproxy2");
   poxy2.Write("here was invoked"); //---> "here was invoked by coreproxy2"

   var poxy3 = ProxyGenerator.Create<targetInterface, SampleProxy>("coreproxy3");
   poxy3.Write("here was invoked"); //---> "here was invoked by coreproxy3"
  }
 }


 public class SampleProxy : IInterceptor
 {
  private string proxyName { get; }

  public SampleProxy(string name)
  {
   this.proxyName = name;
  }

  public object Intercept(MethodInfo method, object[] parameters)
  {
   Console.WriteLine(parameters[0] + " by " + proxyName);
   return null;
  }
 }

 public interface targetInterface
 {
  void Write(string writesome);
 }