Passing none static member function as callback parameter to manag

[Haxan]

Hi,

I have my main application class(unmanaged ) that has a none static member
function that I need to pass as a delegate to managed C# method.

In one of the methods of this class(unmamange d), I am calling a managed C#
method(I use gcnew to instantiate the managed class). One of the parameters
of this C# method is a delegate. I need to pass the none static member
function as a delegate(functi on pointer) as a parameter in the managed C#
function call.

e.g.

//Managed C#
namespace MySpace
{
public delegate int MyDelegate();

MyDelegate rDelegate;

public class Managed
{
void ManagedFunction (MyDelegate del)
{
//do stuff
}

}
}
//Unmanaged C++ written in VC++ 6.0

//.h
class Unmanaged
{
public:
Unmanaged();
~Unmanaged();

void UnmanagedFunc1( );
void UnmanagedFunc2( );

}

*.cpp
using namespace MySpace;

void Unmanaged::Unma nagedFunc1()
{
MySpace::Manage d ^man = gcnew MySpace::Manage d;

//I need to pass UnmanagedFunc2( ) here as a delegate/callback as a
//parameter to ManagedFunction .
man->ManagedFunctio n(??)

}

void Unmanaged::Unma nagedFunc2()
{

}

Will appreciate all the help I can get on this.

Also what if I need to pass a string also as a parameter to
ManagedFunction (). In unmanaged it is a char* or a CString. How can I do the
conversion to pass it to managed.

Thanks for the help.

[Tamas Demjen]

Haxan wrote:

Hi,

I have my main application class(unmanaged ) that has a none static member
function that I need to pass as a delegate to managed C# method.

After some discussion of this topic (see http://tinyurl.com/h2kry), I
came up with two very simple examples demonstrating managed->unmanged
and unmanaged->managed event handling:

http://tweakbits.com/ManagedToUnmanagedCallback.cpp
http://tweakbits.com/UnmanagedToManagedCallback.cpp

What you're asking for is handling managed events from unmanaged code,
so my ManagedToUnmana gedCallback.cpp example should give you an idea.

On the other hand, I assume your code is written in VC++ 2005, compiled
in mixed-mode. It looks like your unmanaged class is written in VC6,
which requires yet another level of interaction. In other words, the
Thunk class (see my example) will call a VC6 DLL inside.

In addition to my example, Microsoft has an official guide about this
subject too:
http://msdn2.microsoft.com/en-us/library/367eeye0.aspx

Finally, you have to take care of your argument marshaling, such as
converting String^ to const char* / const wchar_t*. You can use
StringToHGlobal Ansi/StringToHGlobal Uni to do that, as shown here:
http://tinyurl.com/kmzmh (see Jochen's StringConvA / StringConvW classes).

Tom

[Tamas Demjen]

Tamas Demjen wrote:

which requires yet another level of interaction.

* indirection, I meant.

[Haxan]

Thanks very Tamas. This looks like what I was looking for. Appreciate the
tips. I will work on it.

"Tamas Demjen" wrote:

Tamas Demjen wrote:

which requires yet another level of interaction.

* indirection, I meant.

[Haxan]

Im still having problems with passing char * parameter in my unmanaged code.
This is how I have defined

//Managed C#
namespace MySpace
{
public delegate int MyDelegate(stri ng strMan);

MyDelegate rDelegate;

public class Managed
{
void ManagedFunction (MyDelegate del)
{
//do stuff
}

}
}
//Unmanaged C++ written in VC++ 6.0

//.h
class Unmanaged
{
public:
Unmanaged();
~Unmanaged();

void UnmanagedFunc1( );
static void UnmanagedFunc2( gcroot<System:: String^pUnm);

}

*.cpp
using namespace MySpace;

void Unmanaged::Unma nagedFunc1()
{
MySpace::Manage d ^man = gcnew MySpace::Manage d;

//I need to pass UnmanagedFunc2( ) here as a delegate/callback as a
//parameter to ManagedFunction .
man->ManagedFunctio n(??)

}

void Unmanaged::Unma nagedFunc2(gcro ot<System::Stri ng^pUnm)
{
}

I get ane error C3352 ..The specified function does not match the delegate
type void(System::St ring ^)

Will appreciate if you can provide me some suggestion on how to fix this.

Thanks


"Tamas Demjen" wrote:

Tamas Demjen wrote:

which requires yet another level of interaction.

* indirection, I meant.

[Haxan]

Please note that my unmanaged class is a dll. It seems like we cannot pass
Managed types/objects as parameters in dlls.

"Tamas Demjen" wrote:

Tamas Demjen wrote:

which requires yet another level of interaction.

* indirection, I meant.

[Tamas Demjen]

Haxan wrote:

Please note that my unmanaged class is a dll. It seems like we cannot pass
Managed types/objects as parameters in dlls.

You don't have to. Your managed code can call your unmanaged DLL.

Tom

[Tamas Demjen]

Haxan wrote:

*.cpp
using namespace MySpace;

void Unmanaged::Unma nagedFunc1()
{
MySpace::Manage d ^man = gcnew MySpace::Manage d;

//I need to pass UnmanagedFunc2( ) here as a delegate/callback as a
//parameter to ManagedFunction .
man->ManagedFunctio n(??)

}

The event must be handled by a managed class, which can forward the call
to a native class. I call this trampoline class Thunk. That's where the
translation from String^ to char* takes place:

ref class Thunk
// managed event handler that forwards to unmanaged call
{
public:
void CallbackForward er(String^ s)
{
UnmanagedFunc1( StringConvA(s). c_str());
}
};

where StringConvA is (untested):

struct StringConvA
{
char *szAnsi;
StringConvA(Str ing^ s)
:
szAnsi(static_c ast<char*>(Syst em::Runtime::In teropServices:: Marshal::String ToHGlobalAnsi(s ).ToPointer()))
{}
~StringConvA()
{
System::Runtime ::InteropServic es::Marshal::Fr eeHGlobal(IntPt r(szAnsi));
}
char* c_str() const
{
return szAnsi;
}

};

Tom

[Haxan]

Actually the unmanaged class is part of an old dll that was written using
VC++ 6.0. Since we later on started using managed code, the changes have to
be part of the dll.

"Tamas Demjen" wrote:

Haxan wrote:

Please note that my unmanaged class is a dll. It seems like we cannot pass
Managed types/objects as parameters in dlls.

You don't have to. Your managed code can call your unmanaged DLL.

Tom

[Tamas Demjen]

Haxan wrote:

Actually the unmanaged class is part of an old dll that was written using
VC++ 6.0. Since we later on started using managed code, the changes have to
be part of the dll.

You have to write a mixed-mode DLL, a translation layer between the C#
and the VC6 code. That mixed-mode DLL has to export native functions
that your VC6 code can call. In turn, it will internally set up the
managed event forwarder and calls the managed library function. This
intermediate DLL is necessary, because I don't think you can compile
C++/CLI code from VC6.

Tom