MSIL实用指南-创建对象

创建对象用Newobj指令，它的操作是创建一个新的对象或值类型，并将对象引用的新实例到计算堆栈上。
格式是
Newobj <构造函数>
实例:

ilGenerator.Emit(OpCodes.Newobj, typeof(Uri).GetConstructor(new Type[] { typeof(string)}));

在调用Newobj指令前，需要加载构造函数所需要的参数。

完整程序如下：

using System;
using System.Reflection;
using System.Reflection.Emit;

namespace LX1_ILDemo
{
    class Demo15_NewObj
    {
        static string binaryName = "Demo15_NewObj.exe";
        static string namespaceName = "LX1_ILDemo";
        static string typeName = "NewObjDemo";

        static AssemblyBuilder assemblyBuilder;
        static ModuleBuilder moduleBuilder;
        static TypeBuilder typeBuilder;
        static MethodBuilder mainMethod;
        static ILGenerator ilGenerator;

        static void Emit_ILCode()
        {
            LocalBuilder localBuilderv1 = ilGenerator.DeclareLocal(typeof(Uri));
            ilGenerator.Emit(OpCodes.Ldstr, "http://www.contoso.com/");
            ilGenerator.Emit(OpCodes.Newobj, typeof(Uri).GetConstructor(new Type[] { typeof(string)}));
            ilGenerator.Emit(OpCodes.Stloc_0);
            ilGenerator.Emit(OpCodes.Ldloc_0);
            ilGenerator.Emit(OpCodes.Call, typeof(Console).GetMethod("WriteLine", new Type[] { typeof(object) }));
        }
         
        public static void Generate()
        {
            InitAssembly();

            typeBuilder = moduleBuilder.DefineType(namespaceName + "." + typeName, TypeAttributes.Public);

            GenerateMain();

            Emit_ILCode();

            EmitReadKey();
            ilGenerator.Emit(OpCodes.Ret);

            /*  设置assembly入口方法 */
            assemblyBuilder.SetEntryPoint(mainMethod, PEFileKinds.ConsoleApplication);

            SaveAssembly();
            Console.WriteLine("生成成功");
        }

        static void EmitReadKey()
        {
            /* 生成 Console.ReadKey(); */
            MethodInfo readKeyMethod = typeof(Console).GetMethod("ReadKey", new Type[] { });
            ilGenerator.Emit(OpCodes.Call, readKeyMethod);
            ilGenerator.Emit(OpCodes.Pop);
        }

        static void GenerateMain()
        {
            mainMethod = typeBuilder.DefineMethod("Main", MethodAttributes.Public
                | MethodAttributes.Static, typeof(void), new Type[] { });
            ilGenerator = mainMethod.GetILGenerator();
        }

        static void InitAssembly()
        {
            AssemblyName assemblyName = new AssemblyName(namespaceName);
            assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndSave);
            moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName.Name, binaryName);
        }

        static void SaveAssembly()
        {
            Type t = typeBuilder.CreateType(); //完成Type，这是必须的
            assemblyBuilder.Save(binaryName);
        }
    }
}