Accessing and Unmanaged Class from Managed Code

[Brett Styles]

Hi Guys,
I am trying to access a class in an unmanaged dll. I have
created a wrapper managed class to access the functions I need but no matter
what I try from the MSDN samples I can not get it to work with my code. I
have a VB Net front end which need the access the unmanaged functions. The
wrapper I wrote can be accessed but the wrapper will not compile when I
refer to the unmanaged class. I have tried using header file for definitions
with and #include in the managed code, __dllExport and all my attempts do
not work. I am escentially a VB programmer but have done enough C years ago
to allow me to get the code working stand alone. I am not up to the task at
hand and would really appreciate some ideas from the C++ experts out there.

Thanks
Brett Styles.

snippet:

managed wrapper:

namespace CameraSDK
{
__gc public class CameraManaged
{
public:
CameraManaged(void)
{
}

~CameraManaged(void)
{
}

ConnectCamera()
{
CProg.Connect(); //Error here every time.
}

private:
CameraU CProg; //ERROR here every time
}:
}
Unmanaged Code

class CameraU
{
CameraU::CameraU(void)
{
}

~CameraU::CameraU(void)
{
}

Connect()
{
.......code here
}
};

[Lev]

Hi,

You should use a pointer to the unmanaged class instead of embedding the
unmanaged type in the managed class. Embedding only work in the most trivial
cases, and should you find yourself in such a situation, you are most likely
better off making the class to be embedded either __gc or __value. The
problem is that when you embed an unmanaged object in a managed class, all
the members of the unmanged class will be created on the GC heap (think of
the disastrous effects of for instance a memcpy on the managed heap).
If possible, you should have a pointer to the unmanaged class in the
managed class and new it up from the constructor (or other function) of the
managed class if possible.

Hope this helps,

Lev

"Brett Styles" <br*********@tpg.com.au> wrote in message
news:%2****************@TK2MSFTNGP12.phx.gbl...

Hi Guys,
I am trying to access a class in an unmanaged dll. I have
created a wrapper managed class to access the functions I need but no matter what I try from the MSDN samples I can not get it to work with my code. I
have a VB Net front end which need the access the unmanaged functions. The
wrapper I wrote can be accessed but the wrapper will not compile when I
refer to the unmanaged class. I have tried using header file for definitions with and #include in the managed code, __dllExport and all my attempts do
not work. I am escentially a VB programmer but have done enough C years ago to allow me to get the code working stand alone. I am not up to the task at hand and would really appreciate some ideas from the C++ experts out there.
Thanks
Brett Styles.

snippet:

managed wrapper:

namespace CameraSDK
{
__gc public class CameraManaged
{
public:
CameraManaged(void)
{
}

~CameraManaged(void)
{
}

ConnectCamera()
{
CProg.Connect(); //Error here every time.
}

private:
CameraU CProg; //ERROR here every time
}:
}
Unmanaged Code

class CameraU
{
CameraU::CameraU(void)
{
}

~CameraU::CameraU(void)
{
}

Connect()
{
......code here
}
};

[Brett Styles]

I did not make my example clear. I actually have two
projects one managed (which contains the class CameraManaged) and another
project which is unmanaged but refrenced by the managed one (this contains
the class CameraU). I tried embedding early on but that did not work. Both
operate independently prefectly ok. I just can not create a reference to
the unmanaged class from the managed one, in VB this is a simple task but in
C++ there are so many options I do not know what the errors reported mean
when I try different options as set out in the MSDN samples. One error that
comes up a lot is unreferenced exteral _dtor, when I search I cannot find
any thing that calls such a method.

Regards
Brett