Hi

I have a C# DLL which has a method which accepts a string argument.  This is 
registered for COM.  The resulting .tlb is then referenced in a native C++ 
DLL.  I then wrap the method in a C++ method and add some trace code.  The 
wrapped C# method also includes some trace code.  When I attempt to run the 
C++ method, passing a BSTR to it, the C++ methods trace code fires, however, 
the C# method call doesn't appear to do anything.

The strange thing is that if I remove the string argument from the C# 
method, regenerate the .tlb and change the wrapper method accordingly the C# 
trace code fires.  I have other methods which accept and return numeric 
types which issue, it's just this one which accepts a BSTR that seems to be 
a problem.

I should say that the C++ dll has to be native to integrate with an ancient 
PowerBuilder component which can't be changed, hence the C++ to COM to C# 
process.

I'm rather lost on this one, as I know almost nothing about C++, so I'd 
really appreciate if anyone can give me a few pointers (no pun intended).

Many Thanks

Glenn

GlennAnthonyB wrote:

> Hi
> 
> I have a C# DLL which has a method which accepts a string argument.  This is 
> registered for COM.  The resulting .tlb is then referenced in a native C++ 
> DLL.  I then wrap the method in a C++ method and add some trace code.  The 
> wrapped C# method also includes some trace code.  When I attempt to run the 
> C++ method, passing a BSTR to it, the C++ methods trace code fires, however, 
> the C# method call doesn't appear to do anything.

Does anything mean that the call succeeds though the trace code is not 
executed or does it hang?


> The strange thing is that if I remove the string argument from the C# 
> method, regenerate the .tlb and change the wrapper method accordingly the C# 
> trace code fires.  I have other methods which accept and return numeric 
> types which issue, it's just this one which accepts a BSTR that seems to be 
> a problem.
 >
> I should say that the C++ dll has to be native to integrate with an ancient 
> PowerBuilder component which can't be changed, hence the C++ to COM to C# 
> process.

Can you please post the affected code of both the C# and the C++ side?

--Johannes


-- 
Johannes Passing - http://int3.de/

"Johannes Passing"  wrote in message 
news:O4Vzu7Z4HHA.5880@TK2MSFTNGP03.phx.gbl...

> GlennAnthonyB wrote:
>> Hi
>>
>> I have a C# DLL which has a method which accepts a string argument.  This 
>> is registered for COM.  The resulting .tlb is then referenced in a native 
>> C++ DLL.  I then wrap the method in a C++ method and add some trace code. 
>> The wrapped C# method also includes some trace code.  When I attempt to 
>> run the C++ method, passing a BSTR to it, the C++ methods trace code 
>> fires, however, the C# method call doesn't appear to do anything.
> Does anything mean that the call succeeds though the trace code is not 
> executed or does it hang?


It's doesn't hang, it just doesn't appear to enter the C# method.


>
>> The strange thing is that if I remove the string argument from the C# 
>> method, regenerate the .tlb and change the wrapper method accordingly the 
>> C# trace code fires.  I have other methods which accept and return 
>> numeric types which issue, it's just this one which accepts a BSTR that 
>> seems to be a problem.
> >
>> I should say that the C++ dll has to be native to integrate with an 
>> ancient PowerBuilder component which can't be changed, hence the C++ to 
>> COM to C# process.
> Can you please post the affected code of both the C# and the C++ side?


C# code fragment...

public int Search( string searchString )
{
 Trace.TraceInformation( "Managed Search method invoked..." );

 int status = -1;

 return status;
}

C++ code fragment...

#include "stdafx.h"

#import "Test.tlb" raw_interfaces_only

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
      )
{
 CoInitialize( NULL );
    return TRUE;
}

int Search( BSTR searchString )
{
 long lResult = 0;

 Test::ISearchEnginePtr searchEngine( __uuidof( Test::SearchEngine ) );

 searchEngine->Search( searchString, &lResult );

 printf( "result %d", lResult );

 return lResult;
}



>
> --Johannes
>
>
> -- 
> Johannes Passing - http://int3.de/


Thanks

Glenn

Interesting point is that if I create a BSTR in the C++ method I can pass 
that to the COM wrapped C# method and it works.  The issue is using the BSTR 
argument passed to the C++ method.


"glennanthonyb"  wrote in message 
news:eBWg9Iw4HHA.5160@TK2MSFTNGP05.phx.gbl...

>
> "Johannes Passing"  wrote in message 
> news:O4Vzu7Z4HHA.5880@TK2MSFTNGP03.phx.gbl...
>> GlennAnthonyB wrote:
>>> Hi
>>>
>>> I have a C# DLL which has a method which accepts a string argument. 
>>> This is registered for COM.  The resulting .tlb is then referenced in a 
>>> native C++ DLL.  I then wrap the method in a C++ method and add some 
>>> trace code. The wrapped C# method also includes some trace code.  When I 
>>> attempt to run the C++ method, passing a BSTR to it, the C++ methods 
>>> trace code fires, however, the C# method call doesn't appear to do 
>>> anything.
>> Does anything mean that the call succeeds though the trace code is not 
>> executed or does it hang?
>
> It's doesn't hang, it just doesn't appear to enter the C# method.
>
>>
>>> The strange thing is that if I remove the string argument from the C# 
>>> method, regenerate the .tlb and change the wrapper method accordingly 
>>> the C# trace code fires.  I have other methods which accept and return 
>>> numeric types which issue, it's just this one which accepts a BSTR that 
>>> seems to be a problem.
>> >
>>> I should say that the C++ dll has to be native to integrate with an 
>>> ancient PowerBuilder component which can't be changed, hence the C++ to 
>>> COM to C# process.
>> Can you please post the affected code of both the C# and the C++ side?
>
> C# code fragment...
>
> public int Search( string searchString )
> {
> Trace.TraceInformation( "Managed Search method invoked..." );
>
> int status = -1;
>
> return status;
> }
>
> C++ code fragment...
>
> #include "stdafx.h"
>
> #import "Test.tlb" raw_interfaces_only
>
> BOOL APIENTRY DllMain( HMODULE hModule,
>                       DWORD  ul_reason_for_call,
>                       LPVOID lpReserved
>      )
> {
> CoInitialize( NULL );
>    return TRUE;
> }
>
> int Search( BSTR searchString )
> {
> long lResult = 0;
>
> Test::ISearchEnginePtr searchEngine( __uuidof( Test::SearchEngine ) );
>
> searchEngine->Search( searchString, &lResult );
>
> printf( "result %d", lResult );
>
> return lResult;
> }
>
>
>>
>> --Johannes
>>
>>
>> -- 
>> Johannes Passing - http://int3.de/
>
> Thanks
>
> Glenn
> 

Hi Glenn,

first, there are some issues with your DllMain. DllMain is not only 
called on initialization but also on termination of process/threads, so 
you definitely need to switch on ul_reason_for_call rather than always 
perform the same action. Furthermore, you should never call CoInitialize 
from DllMain - see [1] for details. Depending on the calling 
application, this might even be the reason for your problem, so try to 
fix this first.

To use COM in a DLL, create a helper thread (in the C++ Search function) 
and perform all COM-related work on this thread.

[1] http://download.microsoft.com/download/a/f/7/
af7777e5-7dcd-4800-8a0a-b18336565f5b/DLL_bestprac.doc

--Johannes


> 
> 
> "glennanthonyb"  wrote in message 
> news:eBWg9Iw4HHA.5160@TK2MSFTNGP05.phx.gbl...
>> "Johannes Passing"  wrote in message 
>> news:O4Vzu7Z4HHA.5880@TK2MSFTNGP03.phx.gbl...
>>> GlennAnthonyB wrote:
>>>> Hi
>>>>
>>>> I have a C# DLL which has a method which accepts a string argument. 
>>>> This is registered for COM.  The resulting .tlb is then referenced in a 
>>>> native C++ DLL.  I then wrap the method in a C++ method and add some 
>>>> trace code. The wrapped C# method also includes some trace code.  When I 
>>>> attempt to run the C++ method, passing a BSTR to it, the C++ methods 
>>>> trace code fires, however, the C# method call doesn't appear to do 
>>>> anything.
>>> Does anything mean that the call succeeds though the trace code is not 
>>> executed or does it hang?
>> It's doesn't hang, it just doesn't appear to enter the C# method.
>>
>>>> The strange thing is that if I remove the string argument from the C# 
>>>> method, regenerate the .tlb and change the wrapper method accordingly 
>>>> the C# trace code fires.  I have other methods which accept and return 
>>>> numeric types which issue, it's just this one which accepts a BSTR that 
>>>> seems to be a problem.
>>>>
>>>> I should say that the C++ dll has to be native to integrate with an 
>>>> ancient PowerBuilder component which can't be changed, hence the C++ to 
>>>> COM to C# process.
>>> Can you please post the affected code of both the C# and the C++ side?
>> C# code fragment...
>>
>> public int Search( string searchString )
>> {
>> Trace.TraceInformation( "Managed Search method invoked..." );
>>
>> int status = -1;
>>
>> return status;
>> }
>>
>> C++ code fragment...
>>
>> #include "stdafx.h"
>>
>> #import "Test.tlb" raw_interfaces_only
>>
>> BOOL APIENTRY DllMain( HMODULE hModule,
>>                       DWORD  ul_reason_for_call,
>>                       LPVOID lpReserved
>>      )
>> {
>> CoInitialize( NULL );
>>    return TRUE;
>> }
>>
>> int Search( BSTR searchString )
>> {
>> long lResult = 0;
>>
>> Test::ISearchEnginePtr searchEngine( __uuidof( Test::SearchEngine ) );
>>
>> searchEngine->Search( searchString, &lResult );
>>
>> printf( "result %d", lResult );
>>
>> return lResult;
>> }
>>
>>
>>> --Johannes
>>>
>>>
>>> -- 
>>> Johannes Passing - http://int3.de/
>> Thanks
>>
>> Glenn
>>
> 
> 



-- 
Johannes Passing - http://int3.de/

Thanks for the info, appreciate it.

Glenn

"Johannes Passing"  wrote in message 
news:uv5LuI04HHA.556@TK2MSFTNGP06.phx.gbl...

> Hi Glenn,
>
> first, there are some issues with your DllMain. DllMain is not only called 
> on initialization but also on termination of process/threads, so you 
> definitely need to switch on ul_reason_for_call rather than always perform 
> the same action. Furthermore, you should never call CoInitialize from 
> DllMain - see [1] for details. Depending on the calling application, this 
> might even be the reason for your problem, so try to fix this first.
>
> To use COM in a DLL, create a helper thread (in the C++ Search function) 
> and perform all COM-related work on this thread.
>
> [1] http://download.microsoft.com/download/a/f/7/
> af7777e5-7dcd-4800-8a0a-b18336565f5b/DLL_bestprac.doc
>
> --Johannes
>
>>
>>
>> "glennanthonyb"  wrote in message 
>> news:eBWg9Iw4HHA.5160@TK2MSFTNGP05.phx.gbl...
>>> "Johannes Passing"  wrote in message 
>>> news:O4Vzu7Z4HHA.5880@TK2MSFTNGP03.phx.gbl...
>>>> GlennAnthonyB wrote:
>>>>> Hi
>>>>>
>>>>> I have a C# DLL which has a method which accepts a string argument. 
>>>>> This is registered for COM.  The resulting .tlb is then referenced in 
>>>>> a native C++ DLL.  I then wrap the method in a C++ method and add some 
>>>>> trace code. The wrapped C# method also includes some trace code.  When 
>>>>> I attempt to run the C++ method, passing a BSTR to it, the C++ methods 
>>>>> trace code fires, however, the C# method call doesn't appear to do 
>>>>> anything.
>>>> Does anything mean that the call succeeds though the trace code is not 
>>>> executed or does it hang?
>>> It's doesn't hang, it just doesn't appear to enter the C# method.
>>>
>>>>> The strange thing is that if I remove the string argument from the C# 
>>>>> method, regenerate the .tlb and change the wrapper method accordingly 
>>>>> the C# trace code fires.  I have other methods which accept and return 
>>>>> numeric types which issue, it's just this one which accepts a BSTR 
>>>>> that seems to be a problem.
>>>>>
>>>>> I should say that the C++ dll has to be native to integrate with an 
>>>>> ancient PowerBuilder component which can't be changed, hence the C++ 
>>>>> to COM to C# process.
>>>> Can you please post the affected code of both the C# and the C++ side?
>>> C# code fragment...
>>>
>>> public int Search( string searchString )
>>> {
>>> Trace.TraceInformation( "Managed Search method invoked..." );
>>>
>>> int status = -1;
>>>
>>> return status;
>>> }
>>>
>>> C++ code fragment...
>>>
>>> #include "stdafx.h"
>>>
>>> #import "Test.tlb" raw_interfaces_only
>>>
>>> BOOL APIENTRY DllMain( HMODULE hModule,
>>>                       DWORD  ul_reason_for_call,
>>>                       LPVOID lpReserved
>>>      )
>>> {
>>> CoInitialize( NULL );
>>>    return TRUE;
>>> }
>>>
>>> int Search( BSTR searchString )
>>> {
>>> long lResult = 0;
>>>
>>> Test::ISearchEnginePtr searchEngine( __uuidof( Test::SearchEngine ) );
>>>
>>> searchEngine->Search( searchString, &lResult );
>>>
>>> printf( "result %d", lResult );
>>>
>>> return lResult;
>>> }
>>>
>>>
>>>> --Johannes
>>>>
>>>>
>>>> -- 
>>>> Johannes Passing - http://int3.de/
>>> Thanks
>>>
>>> Glenn
>>>
>>
>>
>
>
> -- 
> Johannes Passing - http://int3.de/