static void Main(string[] args)

        {

            //给字段设置值，并返回

            AssemblyName assemblyName = new AssemblyName("test");

            var assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndSave);

            var module = assemblyBuilder.DefineDynamicModule("test_module");

            var typeBuilder = module.DefineType("produce_123", TypeAttributes.Class | TypeAttributes.Public | TypeAttributes.Sealed);

            var method = typeBuilder.DefineMethod("aa", MethodAttributes.Public, CallingConventions.Standard, typeof(string), new Type[] { typeof(string) });

            var fb = typeBuilder.DefineField("bb", typeof(string), FieldAttributes.Public);

            var li= method.GetILGenerator();

            li.Emit(OpCodes.Ldarg_0);//获取this

            li.Emit(OpCodes.Ldarg_1);//获取aa方法的第一个参数

            li.Emit(OpCodes.Stfld, fb);//设置bb字段的值

            li.Emit(OpCodes.Ldarg_0);//获取this

            li.Emit(OpCodes.Ldfld, fb);//将bb字段压入栈

            li.Emit(OpCodes.Ret);//返回值

            var type = typeBuilder.CreateType();

            var obj=Activator.CreateInstance(type);

            var aa= type.GetMethod("aa").Invoke(obj, new object[] { "aa" });

            Console.WriteLine(aa);

            Console.ReadKey();

        }