MSIL实用指南-字段的加载和保存

字段有静态字段和非静态字段之分，它们的加载保存指令也是不一样的，并且非静态字段要生成this。

静态字段的加载
加载静态字段的指令是Ldsfld。
ilGenerator.Emit(OpCodes.Ldsfld, <FieldBuilder>);
实际例子

ilGenerator.Emit(OpCodes.Ldsfld, areaFieldBuilder);
ilGenerator.Emit(OpCodes.Call, writeStringLineMethod);

静态字段的保存
保存静态字段的指令是Stsfld。
ilGenerator.Emit(OpCodes.Stsfld, <FieldBuilder>);
实际例子

ilGenerator.Emit(OpCodes.Ldstr,"New York");
ilGenerator.Emit(OpCodes.Stsfld, areaFieldBuilder);

实例字段的加载
加载静态字段的指令是Ldsfld，必须要在第一步生成Ldarg_0指令。
ilGenerator.Emit(OpCodes.Ldsfld, <FieldBuilder>);
实际例子

ilGenerator.Emit(OpCodes.Ldarg_0);//生成this
ilGenerator.Emit(OpCodes.Ldfld, areaFieldBuilder);
ilGenerator.Emit(OpCodes.Call, writeStringLineMethod);

实例字段的保存
保存静态字段的指令是Stsfld，必须要在第一步生成Ldarg_0指令。
ilGenerator.Emit(OpCodes.Stsfld, <FieldBuilder>);
实际例子

ilGenerator.Emit(OpCodes.Ldarg_0);//生成this
ilGenerator.Emit(OpCodes.Ldstr, "Tom");
ilGenerator.Emit(OpCodes.Stfld, nameFieldBuilder);

一个完整的程序如下

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

namespace LX1_ILDemo
{
    class Demo09_FieldLoadStorm
    {
        static string binaryName = "Demo09_FieldLoadStorm.dll";
        static string namespaceName = "LX1_ILDemo";
        static string typeName = "FieldLoadStorm";

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

        static void Emit_IL()
        {
            /* protected string Area; */
            FieldBuilder areaFieldBuilder = typeBuilder.DefineField("Area", typeof(string),
                FieldAttributes.Public | FieldAttributes.Static);

            /* private string Name; */
            FieldBuilder nameFieldBuilder = typeBuilder.DefineField("Name", typeof(string), FieldAttributes.Public);

            testMethod = typeBuilder.DefineMethod("Test", MethodAttributes.Public, typeof(void), new Type[] { });
            ilGenerator = testMethod.GetILGenerator();

            MethodInfo writeStringLineMethod = typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) });
            ilGenerator.Emit(OpCodes.Ldstr,"New York");
            ilGenerator.Emit(OpCodes.Stsfld, areaFieldBuilder);

            ilGenerator.Emit(OpCodes.Ldsfld, areaFieldBuilder);
            ilGenerator.Emit(OpCodes.Call, writeStringLineMethod);

            ilGenerator.Emit(OpCodes.Ldarg_0);//生成this
            ilGenerator.Emit(OpCodes.Ldstr, "Tom");
            ilGenerator.Emit(OpCodes.Stfld, nameFieldBuilder);

            ilGenerator.Emit(OpCodes.Ldarg_0);//生成this
            ilGenerator.Emit(OpCodes.Ldfld, areaFieldBuilder);
            ilGenerator.Emit(OpCodes.Call, writeStringLineMethod);

            ilGenerator.Emit(OpCodes.Ret);

        }

        public static void Generate()
        {
            InitAssembly();

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

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

        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);
        }
    }
}