Bug in VC++ 2003: Linker unresolved token when accessing __event between assemblies

[Edward Diener]

Scenario:
base class in one assembly, derived class in another assembly, __event in
base class, testing if event has any handlers in derived class with 'if
(OnTestEvent) { //etc. }'.

Result:
LINK : error LNK2020: unresolved token (0A000004) OnTestEvent
LINK : fatal error LNK1120: 1 unresolved externals

Reproduce:
Create a Blank solution, create two projects, both VC++ Class Library .NET,
call one BaseClass, the other DerivedClass. Create dependency of
DerivedClass project on BaseClass project. Add reference of BaseClass to
DerivedClass.

Files:
--------------
BaseClass.h
--------------
#pragma once
namespace BaseClass
{
public __gc class ABaseClass
{
public:
ABaseClass();
__event System::EventHa ndler * OnTestEvent;
private:
int anInt;
};
}
--------------
BaseClass.cpp
-----------------
#include "stdafx.h"
#include "BaseClass. h"
BaseClass::ABas eClass::ABaseCl ass() : anInt(0)
{
}
------------------
DerivedClass.h
------------------
#pragma once
namespace DerivedClass
{
public __gc class ADerivedClass : public BaseClass::ABas eClass
{
public:
ADerivedClass() ;
void TestEventAccess ();
private:
char ch;
};
}
---------------------
DerivedClass.cp p
---------------------
#include "stdafx.h"
#include "DerivedClass.h "
DerivedClass::A DerivedClass::A DerivedClass() : ch(0)
{
}
void DerivedClass::A DerivedClass::T estEventAccess( )
{
if (OnTestEvent)
{
System::EventAr gs * evargs(new System::EventAr gs);
OnTestEvent(thi s,evargs);
}
}

Comments:
If one leaves out the "if (OnTestEvent)" in the derived class and just
triggers the event, no linker errors occur. However I find it a natural
idiom to test if there are any event handlers so as not to execute code,
which may depend on event handlers existing and being called for an event,
if no event handler exists. Is there any other viable workaround for this
bug other than not to do the test for event handlers existing before
triggering the event ?