.net 反射构造你自己的“匿名”对象

由于近来项目的底层架构某些特殊需求及场景的需要要求动态build一个对象，

属性名称个类与类型都是外界动态传入的。

不多说废话，直接上我最原始的代码：

        public static Type GetMyType()
        {
            string[] namelist = new string[] { "UserName", "UserID" };
            Dictionary<string, Type> dic = new Dictionary<string, Type>();
            dic.Add("UserName", typeof(string));
            dic.Add("UserID", typeof(int));

            string strDynamicModuleName = "jksdynamic";
            string strDynamicClassName = "<>jksdynamci";
            AppDomain currentDomain = System.AppDomain.CurrentDomain;
            AssemblyName assemblyName = new AssemblyName();
            assemblyName.Name = strDynamicModuleName;

            AssemblyBuilder assemblyBuilder = currentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);

            ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule(strDynamicModuleName);

            TypeBuilder typeBuilder = moduleBuilder.DefineType(strDynamicClassName, TypeAttributes.Public);

            Type[] methodArgs = { typeof(string) };

            ConstructorBuilder constructorBuiler = typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, new Type[] { typeof(string), typeof(int) });

            //            typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard);
            //typeBuilder.d
            //动态创建字段
            // FieldBuilder fb = typeBuilder.DefineField(item, typeof(System.String), FieldAttributes.Private);
            //ILGenerator ilg = constructorBuiler.GetILGenerator();//生成 Microsoft 中间语言 (MSIL) 指令
            //ilg.Emit(OpCodes.Ldarg_0);
            //ilg.Emit(OpCodes.Call, typeof(object).GetConstructor(Type.EmptyTypes));
            //ilg.Emit(OpCodes.Ldarg_0);
            //ilg.Emit(OpCodes.Ldarg_1);

            ////ilg.Emit(OpCodes.Stfld);
            //ilg.Emit(OpCodes.Ret);

            int index = 0;
            ILGenerator ilg = constructorBuiler.GetILGenerator();
            foreach (string item in dic.Keys)
            {

                //typeBuilder.DefineConstructor(MethodAttributes.Assembly, CallingConventions.VarArgs, new Type[] { typeof(string), typeof(int) });

                //动态创建字段
                //FieldBuilder fb = typeBuilder.DefineField("_" + item, dic[item], FieldAttributes.Private); 

                //类型的属性成员由两部分组成，一是私有字段，二是访问私有字段的属性包装器。
                //包装器运行时的本质与 Method 一样，即包含 Set_Method 和 Get_Method 两个方法。
                //动态创建字段
                FieldBuilder fieldBuilder = typeBuilder.DefineField(dic[item].Name + "_" + item, dic[item], FieldAttributes.Public);

                //FieldBuilder conFieldBuilder = typeBuilder.DefineField(item.ToLower(), dic[item], FieldAttributes.Public);


                index++;
                ilg.Emit(OpCodes.Ldarg_0);//向MSIL流发送属性实例
                ilg.Emit(OpCodes.Ldarg, index);//将指定索引的参数加到堆栈上。
                ilg.Emit(OpCodes.Stfld, fieldBuilder);//装载字段



                //ilg.Emit(OpCodes.Stfld, fieldBuilder);

                PropertyBuilder propertyBuilder = typeBuilder.DefineProperty(item, PropertyAttributes.None, dic[item], null);
                //MethodAttributes getSetAttr = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig;
                MethodBuilder methodBuilder = typeBuilder.DefineMethod("get_" + item, MethodAttributes.Public, dic[item], null);

                ILGenerator ilGenerator = methodBuilder.GetILGenerator();
                ilGenerator.Emit(OpCodes.Ldarg_0);
                ilGenerator.Emit(OpCodes.Ldfld, fieldBuilder);//装载属性私有字段
                ilGenerator.Emit(OpCodes.Ret);
                propertyBuilder.SetGetMethod(methodBuilder);// 设置获取属性值的方法

                methodBuilder = typeBuilder.DefineMethod("set_" + item,
                               MethodAttributes.Public,
                               typeof(void), new Type[] { dic[item] });

                ilGenerator = methodBuilder.GetILGenerator();
                ilGenerator.Emit(OpCodes.Ldarg_0);
                ilGenerator.Emit(OpCodes.Ldarg_1);
                ilGenerator.Emit(OpCodes.Stfld, fieldBuilder);
                ilGenerator.Emit(OpCodes.Ret);
                propertyBuilder.SetSetMethod(methodBuilder);// 设置属性值的方法


            }
            ilg.Emit(OpCodes.Ret);
            Type type = typeBuilder.CreateType();

            //Type typeDynamic = moduleBuilder.GetType(strDynamicClassName);
            //object objReturn = Activator.CreateInstance(typeDynamic, "Admin", 90);

            object objReturn = Activator.CreateInstance(type, "Admin", 90);

            return type;

        }

特别说：

ldarg.0微软官网上的说明，这里不做翻译比较简单。
NOTE: ldarg.0 holds the "this" reference - ldarg.1, ldarg.2, and ldarg.3
hold the actual passed parameters. ldarg.0 is used by instance methods
to hold a reference to the current calling object instance. Static methods
do not use arg.0, since they are not instantiated and hence no reference
is needed to distinguish them.

测试代码如下：

        public static void TestCreateType()
        {
            Type myDynamicType = GetMyType();
            Console.WriteLine("Some information about my new Type '{0}':",
                              myDynamicType.FullName);
            Console.WriteLine("Assembly: '{0}'", myDynamicType.Assembly);
            Console.WriteLine("Attributes: '{0}'", myDynamicType.Attributes);
            Console.WriteLine("Module: '{0}'", myDynamicType.Module);
            Console.WriteLine("Members: ");
            foreach (MemberInfo member in myDynamicType.GetMembers())
            {
                Console.WriteLine("-- {0} {1};", member.MemberType, member.Name);
            }
            Console.WriteLine("---");
            Type[] aPtypes = new Type[] { typeof(string), typeof(int) };

            object[] aPargs = new object[] { "JksName", 5122 };

            ConstructorInfo myDTctor = myDynamicType.GetConstructor(aPtypes);
            Console.WriteLine("Constructor: {0};", myDTctor.ToString());

            Console.WriteLine("---");

            object amyclass = myDTctor.Invoke(aPargs);
            Console.WriteLine("aPoint is type {0}.", amyclass.GetType());

            //Console.WriteLine("aPoint.x = {0}",
            //                myDynamicType.InvokeMember("get_UserName",
            //                               BindingFlags.InvokeMethod,
            //                               null,
            //                               myDTctor,
            //                               new object[0]));
            Console.WriteLine("Method ---");
            foreach (MethodInfo method in myDynamicType.GetMethods())
            {
                if (method.Name.StartsWith("get_"))
                {
                    object v = method.Invoke(amyclass, null);
                    Console.WriteLine(method.Name + " : " + v.ToString());
                }
            }
            Console.WriteLine("Property ---");
            foreach (PropertyInfo property in myDynamicType.GetProperties())
            {

                Console.WriteLine(property.Name + " : " + property.GetValue(amyclass).ToString());

            }

        }

运行结果如下：