MSIL实用指南-加载bool、sbyte、byte、char、short等值

这一篇讲解怎么加载bool值、sbyte值、byte值、char值、short值。

加载bool值
在.NET程序实际运行中，是没有true和false值的，实际上是以1和0表示它们，加载它们的指令是Ldc_I4_1和Ldc_I4_0。
下面是实际例子：
/* 加载true，即加载1 */
ilGenerator.Emit(OpCodes.Ldc_I4_1);
/* 加载false，即加载0 */
ilGenerator.Emit(OpCodes.Ldc_I4_0);

加载sbyte值
sbyte是8位有符号整数类型，它的加载指令是Ldc_I4_S，格式是
ilGenerator.Emit(OpCodes.Ldc_I4_S, <sbyte值>);
例如:
ilGenerator.Emit(OpCodes.Ldc_I4_S,(sbyte)100);

加载byte值
byte是8位无符号整数类型，加载它实际就是加载整数，加载它用加载前面实现的加载int值的函数
LoadInt(ILGenerator il, int value)就可以。
例如：
LoadInt(ilGenerator, (int)(100));


加载char值
char实际上是16位无符号整数类型，加载它也就是加载整数，加载它用加载前面实现的加载int值的函数
LoadInt(ILGenerator il, int value)就可以。
例如：
LoadInt(ilGenerator, (int)('A'));

加载short值
short是16位有符号整数类型，加载它和加载整数一样，与加载char差不多，加载它用加载前面实现的加载int值的函数
LoadInt(ILGenerator il, int value)就可以。
例如：
LoadInt(ilGenerator, (short)(-100));


完整的程序：

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

namespace LX1_ILDemo
{
    /// <summary>
    /// load char、sbyte、char值
    /// </summary>
    class Demo03_LoadBSBC
    {
        static string binaryName = "Demo03_LoadBSBC.exe";
        static string namespaceName = "LX1_ILDemo";
        static string typeName = "LoadBSBC";

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

        static void Emit_Ldc()
        {
            /* 加载bool值 */
            MethodInfo writeBoolLineMethod = typeof(Console).GetMethod("WriteLine", new Type[] { typeof(bool) });

            /* 加载true，即加载1 */
            ilGenerator.Emit(OpCodes.Ldc_I4_1);
            ilGenerator.Emit(OpCodes.Call, writeBoolLineMethod);

            /* 加载false，即加载0 */
            ilGenerator.Emit(OpCodes.Ldc_I4_0);
            ilGenerator.Emit(OpCodes.Call, writeBoolLineMethod);


            /* 加载sbyte值，用Ldc_I4_S */
            MethodInfo writeIntLineMethod = typeof(Console).GetMethod("WriteLine", new Type[] { typeof(int) });
            ilGenerator.Emit(OpCodes.Ldc_I4_S,(sbyte)100);
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            ilGenerator.Emit(OpCodes.Ldc_I4_S, (sbyte)(-1));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            ilGenerator.Emit(OpCodes.Ldc_I4_S, sbyte.MaxValue);
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            ilGenerator.Emit(OpCodes.Ldc_I4_S, sbyte.MinValue);
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            /* 加载byte值，和加载整数一样 */
            LoadInt(ilGenerator, (int)(101));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            LoadInt(ilGenerator, (int)(byte.MaxValue));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            LoadInt(ilGenerator, (int)(byte.MinValue));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            /* 加载char值，即加载16位无符号整数 */
            MethodInfo writeCharLineMethod = typeof(Console).GetMethod("WriteLine", new Type[] { typeof(char) });
            LoadInt(ilGenerator, (int)('A'));
            ilGenerator.Emit(OpCodes.Call, writeCharLineMethod);

            LoadInt(ilGenerator, (int)('C'));
            ilGenerator.Emit(OpCodes.Call, writeCharLineMethod);

            LoadInt(ilGenerator, (int)(char.MaxValue));
            ilGenerator.Emit(OpCodes.Call, writeCharLineMethod);

            LoadInt(ilGenerator, (int)(char.MinValue));
            ilGenerator.Emit(OpCodes.Call, writeCharLineMethod);

            /* 加载short值，和加载整数一样 */
            LoadInt(ilGenerator, (short)(-100));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            LoadInt(ilGenerator, (short)(100));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            LoadInt(ilGenerator, (int)(short.MaxValue));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);

            LoadInt(ilGenerator, (int)(short.MinValue));
            ilGenerator.Emit(OpCodes.Call, writeIntLineMethod);
        }

        public static void LoadInt(ILGenerator il, int value)
        {
            switch (value)
            {
                case -1:
                    il.Emit(OpCodes.Ldc_I4_M1);
                    return;
                case 0:
                    il.Emit(OpCodes.Ldc_I4_0);
                    return;
                case 1:
                    il.Emit(OpCodes.Ldc_I4_1);
                    return;
                case 2:
                    il.Emit(OpCodes.Ldc_I4_2);
                    return;
                case 3:
                    il.Emit(OpCodes.Ldc_I4_3);
                    return;
                case 4:
                    il.Emit(OpCodes.Ldc_I4_4);
                    return;
                case 5:
                    il.Emit(OpCodes.Ldc_I4_5);
                    return;
                case 6:
                    il.Emit(OpCodes.Ldc_I4_6);
                    return;
                case 7:
                    il.Emit(OpCodes.Ldc_I4_7);
                    return;
                case 8:
                    il.Emit(OpCodes.Ldc_I4_8);
                    return;
            }

            if (value > -129 && value < 128)
            {
                il.Emit(OpCodes.Ldc_I4_S, (SByte)value);
            }
            else
            {
                il.Emit(OpCodes.Ldc_I4, value);
            }
        }

        public static void Generate()
        {
            InitAssembly();

            /* 生成 public class LoadLFDSN */
            typeBuilder = moduleBuilder.DefineType( namespaceName+"."+ typeName, TypeAttributes.Public);

            /* 生成 public static void Main() */
            GenerateMain();

            Emit_Ldc();

            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);
        }
    }
}