IsConst Class
Assembly: mscorlib (in mscorlib.dll)
The Microsoft C++ compiler emits this modifier into metadata for any parameter, return type, or object declaration declared as const in the source code.
Compilers emit custom modifiers within metadata to change the way that the just-in-time (JIT) compiler handles values when the default behavior is not appropriate. When the JIT compiler encounters a custom modifier, it handles the value in the way that the modifier specifies. Compilers can apply custom modifiers to methods, parameters, and return values. The JIT compiler must respond to required modifiers but can ignore optional modifiers.
You can emit custom modifiers into metadata using one of the following techniques:
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Using methods in the TypeBuilder class such as DefineMethod, DefineField, DefineConstructor, and DefineProperty.
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Generating a Microsoft intermediate language (MSIL) instruction file that contains calls to modopt and modreq, and assembling the file with the MSIL Assembler (Ilasm.exe).
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Using the unmanaged reflection API.
The following example demonstrates how to emit an IsConst object into an assembly using reflection.
#using <mscorlib.dll> using namespace System; using namespace System::Reflection; using namespace System::Reflection::Emit; using namespace System::Runtime::CompilerServices; using namespace System::Threading; ref class CodeEmitter { private: AssemblyBuilder^ asmBuilder; String^ asmName; ModuleBuilder^ modBuilder; void prepareAssembly(String^ name){ // Check the input. if(!name){ throw gcnew ArgumentNullException("AssemblyName"); } asmName = name; // Create an AssemblyName object and set the name. AssemblyName^ asmName = gcnew AssemblyName(); asmName->Name = name; // Use the AppDomain class to create an AssemblyBuilder instance. AppDomain^ currentDomain = Thread::GetDomain(); asmBuilder = currentDomain->DefineDynamicAssembly(asmName,AssemblyBuilderAccess::RunAndSave); // Create a dynamic module. modBuilder = asmBuilder->DefineDynamicModule(name); } public: // Constructor. CodeEmitter(String ^ AssemblyName){ prepareAssembly(AssemblyName); } // Create a new type. TypeBuilder^ CreateType(String^ name){ // Check the input. if(!name){ throw gcnew ArgumentNullException("AssemblyName"); } return modBuilder->DefineType( name ); } // Write the assembly. void WriteAssembly(MethodBuilder^ entryPoint){ // Check the input. if(!entryPoint){ throw gcnew ArgumentNullException("entryPoint"); } asmBuilder->SetEntryPoint( entryPoint ); asmBuilder->Save( asmName ); } }; void main() { // Create a CodeEmitter to handle assembly creation. CodeEmitter ^ e = gcnew CodeEmitter("program.exe"); // Create a new type. TypeBuilder^ mainClass = e->CreateType("MainClass"); // Create a new method. MethodBuilder^ mBuilder = mainClass->DefineMethod("mainMethod", MethodAttributes::Static); // Create an ILGenerator and emit IL for // a simple "Hello World." program. ILGenerator^ ilGen = mBuilder->GetILGenerator(); ilGen->Emit(OpCodes::Ldstr, "Hello World"); array<Type^>^mType = {String::typeid}; MethodInfo^ writeMI = Console::typeid->GetMethod( "WriteLine", mType ); ilGen->EmitCall(OpCodes::Call, writeMI, nullptr ); ilGen->Emit( OpCodes::Ret ); ///////////////////////////////////////////////// ///////////////////////////////////////////////// // Apply a required custom modifier // to a field. ///////////////////////////////////////////////// ///////////////////////////////////////////////// array<Type^>^fType = {IsConst::typeid}; mainClass->DefineField("modifiedInteger", Type::GetType("System.Int32"), fType, nullptr, FieldAttributes::Private); // Create the type. mainClass->CreateType(); // Write the assembly using a reference to // the entry point. e->WriteAssembly(mBuilder); Console::WriteLine(L"Assembly created."); }
Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.