using System;using System.Linq;using System.Reflection;using System.Reflection.Emit;namespace EmitCreateDynamicProxy{    class Program    {        static void Main(string[] args)        {            var command = Proxy.Of();            command.Execute();            Console.ReadLine();        }    }    public class Command    {        public virtual void Execute()        {            Console.WriteLine("Hello Kitty!");        }    }     public class Interceptor    {        public object Invoke(object @object, string @method, object[] parameters)        {            Console.WriteLine(              string.Format(" before invoke [{0}]...", @method));            var retObj = @object.GetType().GetMethod(@method).Invoke(@object, parameters);            Console.WriteLine(              string.Format(" after invoke [{0}]...", @method));            return retObj;        }    }    public class Proxy    {        public static T Of
     
      ()         {            string nameOfAssembly = typeof(T).Name + "ProxyAssembly";            string nameOfModule = typeof(T).Name + "ProxyModule";            string nameOfType = typeof(T).Name + "Proxy";            var assemblyName = new AssemblyName(nameOfAssembly);            var assembly = AppDomain.CurrentDomain              .DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);            var moduleBuilder = assembly.DefineDynamicModule(nameOfModule);                      var typeBuilder = moduleBuilder.DefineType(              nameOfType, TypeAttributes.Public,typeof(T));            InjectInterceptor
      
       (typeBuilder);            var t = typeBuilder.CreateType();            return (T)Activator.CreateInstance(t) ;        }        private static void InjectInterceptor
       
        (TypeBuilder typeBuilder)        {            // ---- define fields ----            var fieldInterceptor = typeBuilder.DefineField(              "_interceptor", typeof(Interceptor), FieldAttributes.Private);            // ---- define costructors ----            var constructorBuilder = typeBuilder.DefineConstructor(              MethodAttributes.Public, CallingConventions.Standard, null);            var ilOfCtor = constructorBuilder.GetILGenerator();            ilOfCtor.Emit(OpCodes.Ldarg_0);            ilOfCtor.Emit(OpCodes.Newobj, typeof(Interceptor).GetConstructor(new Type[0]));            ilOfCtor.Emit(OpCodes.Stfld, fieldInterceptor);            ilOfCtor.Emit(OpCodes.Ret);            // ---- define methods ----            var methodsOfType = typeof(T).GetMethods(BindingFlags.Public | BindingFlags.Instance);            for (var i = 0; i < methodsOfType.Length; i++)            {                var method = methodsOfType[i];                var methodParameterTypes =                  method.GetParameters().Select(p => p.ParameterType).ToArray();                var methodBuilder = typeBuilder.DefineMethod(                  method.Name,                  MethodAttributes.Public | MethodAttributes.Virtual,                  CallingConventions.Standard,                  method.ReturnType,                  methodParameterTypes);                var ilOfMethod = methodBuilder.GetILGenerator();                ilOfMethod.Emit(OpCodes.Ldarg_0);                ilOfMethod.Emit(OpCodes.Ldfld, fieldInterceptor);                // create instance of T              ilOfMethod.Emit(OpCodes.Newobj, typeof(T).GetConstructor(new Type[0]));               ilOfMethod.Emit(OpCodes.Ldstr, method.Name);                // build the method parameters                if (methodParameterTypes == null)                {                    ilOfMethod.Emit(OpCodes.Ldnull);                }                else                {                    var parameters = ilOfMethod.DeclareLocal(typeof(object[]));                    ilOfMethod.Emit(OpCodes.Ldc_I4, methodParameterTypes.Length);                    ilOfMethod.Emit(OpCodes.Newarr, typeof(object));                    ilOfMethod.Emit(OpCodes.Stloc, parameters);                    for (var j = 0; j < methodParameterTypes.Length; j++)                    {                        ilOfMethod.Emit(OpCodes.Ldloc, parameters);                        ilOfMethod.Emit(OpCodes.Ldc_I4, j);                        ilOfMethod.Emit(OpCodes.Ldarg, j + 1);                        ilOfMethod.Emit(OpCodes.Stelem_Ref);                    }                    ilOfMethod.Emit(OpCodes.Ldloc, parameters);                }                // call Invoke() method of Interceptor                ilOfMethod.Emit(OpCodes.Callvirt, typeof(Interceptor).GetMethod("Invoke"));                // pop the stack if return void                if (method.ReturnType == typeof(void))                {                    ilOfMethod.Emit(OpCodes.Pop);                }                // complete                ilOfMethod.Emit(OpCodes.Ret);            }        }    }}