Windows apps
Collapse the table of content
Expand the table of content
Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

ILGenerator::BeginFaultBlock Method ()

 

Begins an exception fault block in the Microsoft intermediate language (MSIL) stream.

Namespace:   System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

public:
virtual void BeginFaultBlock()

Exception Condition
NotSupportedException

The MSIL being generated is not currently in an exception block.

-or-

This ILGenerator belongs to a DynamicMethod.

If the current ILGenerator is associated with a DynamicMethod object, emitting exception fault blocks is not supported. DynamicILInfo can be used to construct a dynamic method that uses exception fault blocks.

The following code sample illustrates the use of BeginFaultBlock.

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;

Type^ AddType()
{
   // Create an assembly.
   AssemblyName^ myAssemblyName = gcnew AssemblyName;
   myAssemblyName->Name = "AdderExceptionAsm";

   // Create dynamic assembly.
   AppDomain^ myAppDomain = Thread::GetDomain();
   AssemblyBuilder^ myAssemblyBuilder = myAppDomain->DefineDynamicAssembly( myAssemblyName, AssemblyBuilderAccess::Run );

   // Create a dynamic module.
   ModuleBuilder^ myModuleBuilder = myAssemblyBuilder->DefineDynamicModule( "AdderExceptionMod" );
   TypeBuilder^ myTypeBuilder = myModuleBuilder->DefineType( "Adder" );
   array<Type^>^myAdderParams = {int::typeid,int::typeid};

   // Method to add two numbers.
   MethodBuilder^ myMethodBuilder = myTypeBuilder->DefineMethod( "DoAdd", static_cast<MethodAttributes>(MethodAttributes::Public | MethodAttributes::Static), int::typeid, myAdderParams );
   ILGenerator^ myAdderIL = myMethodBuilder->GetILGenerator();

   // Create constructor.
   array<Type^>^temp0 = {String::typeid};
   ConstructorInfo^ myConstructorInfo = OverflowException::typeid->GetConstructor( temp0 );
   MethodInfo^ myExToStrMI = OverflowException::typeid->GetMethod( "ToString" );
   array<Type^>^temp1 = {String::typeid,Object::typeid};
   MethodInfo^ myWriteLineMI = Console::typeid->GetMethod( "WriteLine", temp1 );

   // Declare local variable.
   LocalBuilder^ myLocalBuilder1 = myAdderIL->DeclareLocal( int::typeid );
   LocalBuilder^ myLocalBuilder2 = myAdderIL->DeclareLocal( OverflowException::typeid );

   // Define label.
   Label myFailedLabel = myAdderIL->DefineLabel();
   Label myEndOfMethodLabel = myAdderIL->DefineLabel();

   // Begin exception block.
   Label myLabel = myAdderIL->BeginExceptionBlock();
   myAdderIL->Emit( OpCodes::Ldarg_0 );
   myAdderIL->Emit( OpCodes::Ldc_I4_S, 10 );
   myAdderIL->Emit( OpCodes::Bgt_S, myFailedLabel );
   myAdderIL->Emit( OpCodes::Ldarg_1 );
   myAdderIL->Emit( OpCodes::Ldc_I4_S, 10 );
   myAdderIL->Emit( OpCodes::Bgt_S, myFailedLabel );
   myAdderIL->Emit( OpCodes::Ldarg_0 );
   myAdderIL->Emit( OpCodes::Ldarg_1 );
   myAdderIL->Emit( OpCodes::Add_Ovf_Un );
   myAdderIL->Emit( OpCodes::Stloc_S, myLocalBuilder1 );
   myAdderIL->Emit( OpCodes::Br_S, myEndOfMethodLabel );
   myAdderIL->MarkLabel( myFailedLabel );
   myAdderIL->Emit( OpCodes::Ldstr, "Cannot accept values over 10 for addition." );
   myAdderIL->Emit( OpCodes::Newobj, myConstructorInfo );
   myAdderIL->Emit( OpCodes::Stloc_S, myLocalBuilder2 );
   myAdderIL->Emit( OpCodes::Ldloc_S, myLocalBuilder2 );

   // Call fault block.
   myAdderIL->BeginFaultBlock();
   Console::WriteLine( "Fault block called." );

   //Throw exception.
   myAdderIL->ThrowException( NotSupportedException::typeid );

   // Call finally block.
   myAdderIL->BeginFinallyBlock();
   myAdderIL->Emit( OpCodes::Ldstr, "{0}" );
   myAdderIL->Emit( OpCodes::Ldloc_S, myLocalBuilder2 );
   myAdderIL->EmitCall( OpCodes::Callvirt, myExToStrMI, nullptr );
   myAdderIL->EmitCall( OpCodes::Call, myWriteLineMI, nullptr );
   myAdderIL->Emit( OpCodes::Ldc_I4_M1 );
   myAdderIL->Emit( OpCodes::Stloc_S, myLocalBuilder1 );

   // End exception block.
   myAdderIL->EndExceptionBlock();
   myAdderIL->MarkLabel( myEndOfMethodLabel );
   myAdderIL->Emit( OpCodes::Ldloc_S, myLocalBuilder1 );
   myAdderIL->Emit( OpCodes::Ret );
   return myTypeBuilder->CreateType();
}

int main()
{
   Type^ myAddType = AddType();
   Object^ myObject1 = Activator::CreateInstance( myAddType );
   array<Object^>^myObject2 = {11,12};

   // Invoke member.
   myAddType->InvokeMember( "DoAdd", BindingFlags::InvokeMethod, nullptr, myObject1, myObject2 );
}

.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Return to top
Show:
© 2017 Microsoft