MSIL实用指南-数学运算

C#支持的数学运算是加、减、乘、除、取模，它们对应的指令是
Add、Sub、Mul、Div、Rem。

这五个运算都需要两个参数，它们的通用步骤
1.生成加载左边变量
2.生成加载右边变量
3.生成运算指令

实例：

ilGenerator.Emit(OpCodes.Ldarg_0);
ilGenerator.Emit(OpCodes.Ldarg_1);
ilGenerator.Emit(OpCodes.Sub);

完整的程序如下：

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

namespace LX1_ILDemo
{
    class Demo16_NumberOP
    {
        static string binaryName = "Demo16_NumberOP.exe";
        static string namespaceName = "LX1_ILDemo";
        static string typeName = "NumberOPDemo";

        static AssemblyBuilder assemblyBuilder;
        static ModuleBuilder moduleBuilder;
        static TypeBuilder typeBuilder;
        static MethodBuilder mainMethod;
        static MethodBuilder testMethod;

        static void Emit_Test()
        {
            testMethod = typeBuilder.DefineMethod("TestOP", MethodAttributes.Public
                | MethodAttributes.Static, typeof(void), new Type[] {typeof(double), typeof(double)});
            var println= typeof(Console).GetMethod("WriteLine", new Type[] { typeof(double) });
            var ilGenerator = testMethod.GetILGenerator();
            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Ldarg_1);
            ilGenerator.Emit(OpCodes.Add);
            ilGenerator.Emit(OpCodes.Call, println);

            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Ldarg_1);
            ilGenerator.Emit(OpCodes.Sub);
            ilGenerator.Emit(OpCodes.Call, println);

            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Ldarg_1);
            ilGenerator.Emit(OpCodes.Mul);
            ilGenerator.Emit(OpCodes.Call, println);

            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Ldarg_1);
            ilGenerator.Emit(OpCodes.Div);
            ilGenerator.Emit(OpCodes.Call, println);

            ilGenerator.Emit(OpCodes.Ldarg_0);
            ilGenerator.Emit(OpCodes.Ldarg_1);
            ilGenerator.Emit(OpCodes.Rem);
            ilGenerator.Emit(OpCodes.Call, println);

            ilGenerator.Emit(OpCodes.Ret);
        }

        public static void Generate()
        {
            InitAssembly();
            typeBuilder = moduleBuilder.DefineType(namespaceName + "." + typeName, TypeAttributes.Public);
            Emit_Test();
            GenerateMain();
            assemblyBuilder.SetEntryPoint(mainMethod, PEFileKinds.ConsoleApplication);
            SaveAssembly();
            Console.WriteLine("生成成功");
        }

        static void GenerateMain()
        {
            mainMethod = typeBuilder.DefineMethod("Main", MethodAttributes.Public
                | MethodAttributes.Static, typeof(void), new Type[] { });
            var ilGenerator = mainMethod.GetILGenerator();
            ilGenerator.Emit(OpCodes.Ldc_R8,(double)1000);
            ilGenerator.Emit(OpCodes.Ldc_R8, (double)2000);
            ilGenerator.Emit(OpCodes.Call, testMethod);

            ilGenerator.Emit(OpCodes.Call, typeof(Console).GetMethod("ReadKey", new Type[] { }));
            ilGenerator.Emit(OpCodes.Pop);
            ilGenerator.Emit(OpCodes.Ret);
        }

        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);
        }
    }
}