VC6 <-> C#(net 2.0) interaction

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Elmar - 13 Jun 2007 12:49 GMT

Hi there.

We maintain a big VC6 project that we currently can´t convert to VS2005 for
various reasons. For our current project we need to establish a communication
channel between this VC6 project and another project that is running on
VS2005 C# and NET 2.0.

All our efforts so far were unsuccessful. Especially triggering events from
C++ to NET doesn´t work. We would be very thankfull for a set of sample
projects that actually interact VC6 <-> C#. Any help would be very
appreciated!

Thanks a lot!

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Jochen Kalmbach [MVP] - 13 Jun 2007 13:09 GMT

Hi Elmar!

> We maintain a big VC6 project that we currently can´t convert to VS2005 for
> various reasons. For our current project we need to establish a communication
[quoted text clipped - 5 lines]
> projects that actually interact VC6 <-> C#. Any help would be very
> appreciated!

What is this VC6 project??? DLL/LIB/EXE/(In/Out)COM-Server ?

Greetings
Jochen

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Elmar - 13 Jun 2007 14:22 GMT

Hi Jochen.

It is an EXE-File.

Thanks.
Elmar

> What is this VC6 project??? DLL/LIB/EXE/(In/Out)COM-Server ?
>
> Greetings
> Jochen

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Bruno van Dooren - 13 Jun 2007 13:10 GMT

> We maintain a big VC6 project that we currently can´t convert to VS2005
> for
[quoted text clipped - 8 lines]
> projects that actually interact VC6 <-> C#. Any help would be very
> appreciated!

There are 2 ways:

1)build a plain C style DLL that communicates with your C++ app in whatever
way you see fit, and then consume that DLL in your .NET app.
.NET 2.0 has facilities for converting delegates to C style function
pointers so with some decent plumbing code, your should be able to make it
work.

2)build a .NET class library that communicates with your .NET app, and
register is for COM interop. then consume that COM class in your C++
application to work with the .NET application.

either way should work without too many problems.

Signature

Kind regards,
Bruno van Dooren MVP - VC++
http://msmvps.com/blogs/vanDooren
bruno_nos_pam_van_dooren@hotmail.com

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Elmar - 13 Jun 2007 15:24 GMT

Can we discuss this a little bit more?
Assuming I have a simple test class library with one class:

------
using System;
using System.Collections.Generic;
using System.Text;

namespace vc6interop
{
public class Interop
{
public static string GreetMe(string name)
{
return "Hallo " + name;
}
}
}
------

...that is compiled with "expose as COM" flag turned on.
What do I have to do in order to call this method in C++?

I found some code that would fit this sample but it gives me a lot of errors.

------
GreetMe function;
CString result;

HINSTANCE hinstLib = LoadLibrary("vc6interop.dll");

if (hinstLib) {

    function = (GreetMe) GetProcAddress(hinstLib, "GreetMe");

    if (function)
        result = (function) ("John");

    BOOL fFreeResult = FreeLibrary(hinstLib);
}

// Das Ergebnis anzeigen
if (!hinstLib || !function)
    printf("Error\n");
else
    printf("Result: %s\n", result);
------

> 2)build a .NET class library that communicates with your .NET app, and
> register is for COM interop. then consume that COM class in your C++
> application to work with the .NET application.
>
> either way should work without too many problems.

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Ben Voigt [C++ MVP] - 13 Jun 2007 18:08 GMT

> Can we discuss this a little bit more?
> Assuming I have a simple test class library with one class:
[quoted text clipped - 24 lines]
> ------
> GreetMe function;

Don't know what that means.

> CString result;
>
> HINSTANCE hinstLib = LoadLibrary("vc6interop.dll");

Nope, only .NET framework can load a .NET assembly.

> if (hinstLib) {
>
> function = (GreetMe) GetProcAddress(hinstLib, "GreetMe");

Nope, .NET code doesn't have an address until the JIT compiles it.

Instead, you must use CoInitialize to enable COM support in your
application, and CoCreateObject to create an instance of a .NET class. Then
you will be able to call the methods.

> if (function)
> result = (function) ("John");
[quoted text clipped - 14 lines]
>>
>> either way should work without too many problems.

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VC6 <-> C#(net 2.0) interaction

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