精通C#---CIL和动态程序集作用

1.托管编译器把.cs编译为 CIL，类型元数据，程序集清单。
2.
CIL不允许直接访问一个数据。
为了实现访问，需要显示的加载数据到栈中。并在使用时弹出。

编写.cs
用ildasm打开，并转储为.il
打开.il，并编辑保存
用ilasm编译.il，形成.exe
用peverify从语义上验证.exe.

4.System.Reflection.Emit使得在运行时，创建程序集及其模块，类型定义以及CIL实现逻辑成为可能。

AssemblyBuilder
ModuleBuilder
EnumBuilder
MethodBuilder
LocalBuilder
PropertyBuilder
FieldBuilder
ConstructorBuilder
CustomAttributeBuilder
ParameterBuilder
EventBuilder
EventBuilder
ILGenerator
OpCodes

System.Reflection.Emit.ILGenerator
// ConstructorBuilder myCtorBuilder = new ConstructorBuilder(/**/);
// ILGenerator myCILGen = myCtorBuilder.GetILGenerator();

BeginCatchBlock
BeginExceptionBlock
BeginFinallyBlock
BeginScope
DeclareLocal
DefineLabel
Emit
EmitCall
EmitWriteLine
EndExceptionBlock
EndScope
ThrowException
UsingNamespace


public class Hello
{
	private string theMessage;
	Hello(){}
	Hello(string s){ theMessage = s; }
	public string GetMsg(){ return theMessage; }
	public void SayHello()
	{
		System.Console.WriteLine("Hello");
	}

	public static void CreateMyAsm(AppDomain curAppDomain)
	{
		AssemblyName assemblyName = new AssemblyName();
		assemblyName.Name = "MyAssembly";
		assemblyName.Version = new Version("1.0.0.0");
		AssemblyBuilder assembly = curAppDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Save);
		ModuleBuilder module = assembly.DefineDynamicModule("MyAssembly", "MyAssembly.dll");

		TypeBuilder helloClass = module.DefineType("MyAssembly.Hello", TypeAttributes.Public);
		FieldBuilder msgField = helloClass.DefineField("theMessage", Type.GetType("System.String"), FieldAttributes.Private);

		Type[] constructorArgs = new Type[1];
		constructorArgs[0] = typeof(string);
		ConstructorBuilder constructor = helloClass.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, constructorArgs);
		ILGenerator constructorIL = constructor.GetILGenerator();
		constructorIL.Emit(OpCodes.Ldarg_0);
		Type objectClass = typeof(object);
		ConstructorInfo superConstructor = objectClass.GetConstructor(new Type[0]);
		constructorIL.Emit(OpCodes.Call, superConstructor);
		constructorIL.Emit(OpCodes.Ldarg_0);
		constructorIL.Emit(OpCodoes.Ldarg_1);
		constructorIL.Emit(OpCodes.Stfld, msgField);
		constructorIL.Emit(OpCodes.Ret);

		helloClass.DefineDefaultConstructor(MethodAttributes.Public);
		MethodBuilder getMsgMethod = helloClass.DefineMethod("GetMsg", MethodAttributes.Public, typeof(string), null);
		ILGenerator methodIL = getMsgMethod.GetILGenerator();
		methodIL.Emit(OpCodes.Ldarg_0);
		methodIL.Emit(OpCodes.Ldfld, msgField);
		methodIL.Emit(OpCodes.Ret);

		MethodBuilder sayHiMethod = helloClass.DefineMethod("SayHello", MethodAttributes.Public, null, null);
		methodIL = sayHiMethod.GetILGenerator();
		methodIL.EmitWriteLine("Hello from the HelloWrold class!");
		methodIL.Emit(OpCodes.Ret);

		helloClass.CreateType();
		assembly.Save("MyAssembly.dll");
	}

	static void Main()
	{
		AppDomain curAppDomain = Thread.GetDomain();
		CreateMyAsm(curAppDomain);
		Console.WriteLine("->Finished creating MyAssembly.dll");
		Assembly a = Assembly.Load("MyAssembly");
		Type hello = a.GetType("MyAssembly.HelloWorld");
		string msg = Console.ReadLine();
		object[] ctorArgs = new object[1];
		ctorArgs[0] = msg;
		object obj = Activator.CreateInstance(hello, ctorArgs);
		MethodInfo mi = hello.GetMethod("SayHello");
		mi.Invoke(obj, null);

		mi = hello.GetMethod("GetMsg");
		Console.WriteLine(mi.Invoke(obj, null));
	}
}