IsLong Class
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IsLong Class


Indicates that a modified integer is a standard C++ long value. This class cannot be inherited.

Namespace:   System.Runtime.CompilerServices
Assembly:  mscorlib (in mscorlib.dll)


public static class IsLong

The C++ standard indicates that a long value and an integer value are distinct types. However, they are both represented using ELEMENT_TYPE_I4 in an assembly. To distinguish a long from an integer in C++, the Microsoft C++ compiler adds the IsLong modifier to any instance of a long when the instance is emited. This process is critically important for maintaining language-level type safety.

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:

The following example demonstrates how to emit an IsLong 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
    AssemblyBuilder^ asmBuilder;
    String^ asmName;
    ModuleBuilder^ modBuilder;

    void prepareAssembly(String^ name){

        // Check the input.

            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);


    // Constructor.
    CodeEmitter(String ^ AssemblyName){


    // Create a new type.
    TypeBuilder^ CreateType(String^ name){

        // Check the input.

            throw gcnew ArgumentNullException("AssemblyName");

        return modBuilder->DefineType( name );

    // Write the assembly.
    void WriteAssembly(MethodBuilder^ entryPoint){

        // Check the input.

            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 = {IsLong::typeid};

    mainClass->DefineField("modifiedInteger", Type::GetType("System.Int64"), fType, nullptr, FieldAttributes::Private);

    // Create the type.

    // Write the assembly using a reference to 
    // the entry point.

    Console::WriteLine(L"Assembly created.");

.NET Framework
Available since 2.0
Available since 2.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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