Forward declaration of C# types in managed C++ headers

[Eckart Haug]

I'm working with C# objects from managed C++ using the gcroot template.
There'a a C++ header containing the definition of a C++ class:

#using <mscorlib.dll>
#include <vcclr.h>
#using <CSharpModule.dll>

class CPlusPlusClass
{
....

gcroot<TLNameSpace::SubNameSpace::SomeType*> _csharpInstance;

....
}
and a C++ source file containing the class definition
#include "CPlusPlusClass.h"
using namespace TLNameSpace::SubNameSpace;
void CPlusPlusClass::createCSharp()
{
gcroot = new SomeType();
}

void CPlusPlusClass::doSomething()
{
gcroot->someCSharpMethod();
}

.....
In this example, I need the #using <CSharpModule.dll> directive in the C++ header. One way to avoid this is
to split CPlusPlusClass into CPlusPlusInterface and CPlusPlus Implementation.
A more elegant technique in C++ would be a forward declaration for TLNameSpace::SubNameSpace::SomeType in
the C++ header. However, I didn't find out how to do this.
The most promising try was

namespace TLNameSpace {
namespace SubNameSpace {
__gcc class SomeType;
}
}

At least the header compiled. On the #using <CSharpModule.dll> line, I got an 'already defined' error.
Obviously C++ and C# namespaces are just a little bit the same ....

My question is:

- Is there a way to do the forward declaration described above ?
I'd appreciate any hint/solution for this

[Vladimir Nesterovsky]

You can add your C# assembly in a project's references thus you may not
import it explicitly.
--
Vladimir Nesterovsky
e-mail: vl******@nesterovsky-bros.com
home: http://www.nesterovsky-bros.com

I'm working with C# objects from managed C++ using the gcroot template.
There'a a C++ header containing the definition of a C++ class:

#using <mscorlib.dll>
#include <vcclr.h>
#using <CSharpModule.dll>

class CPlusPlusClass
{
....

gcroot<TLNameSpace::SubNameSpace::SomeType*> _csharpInstance;

....
}
and a C++ source file containing the class definition
#include "CPlusPlusClass.h"
using namespace TLNameSpace::SubNameSpace;
void CPlusPlusClass::createCSharp()
{
gcroot = new SomeType();
}

void CPlusPlusClass::doSomething()
{
gcroot->someCSharpMethod();
}

.....
In this example, I need the #using <CSharpModule.dll> directive in the C++
header. One way to avoid this is
to split CPlusPlusClass into CPlusPlusInterface and CPlusPlus
Implementation.
A more elegant technique in C++ would be a forward declaration for
TLNameSpace::SubNameSpace::SomeType in
the C++ header. However, I didn't find out how to do this.
The most promising try was

namespace TLNameSpace {
namespace SubNameSpace {
__gcc class SomeType;
}
}

At least the header compiled. On the #using <CSharpModule.dll> line, I got
an 'already defined' error.
Obviously C++ and C# namespaces are just a little bit the same ....

My question is:

- Is there a way to do the forward declaration described above ?
I'd appreciate any hint/solution for this

[Eckart Haug]

Thanx for the quick reply. Your suggestion would mean that I'd have to add a C# reference to any C++ module
that includes the C++ header. There's lots of them and I'd (for the moment) like to have the C++ <-> C#
interface encapsulated in one C++ module.

Vladimir Nesterovsky wrote:

You can add your C# assembly in a project's references thus you may not
import it explicitly.
--
Vladimir Nesterovsky
e-mail: vl******@nesterovsky-bros.com
home: http://www.nesterovsky-bros.com

I'm working with C# objects from managed C++ using the gcroot template.
There'a a C++ header containing the definition of a C++ class:

#using <mscorlib.dll>
#include <vcclr.h>
#using <CSharpModule.dll>

class CPlusPlusClass
{
....

gcroot<TLNameSpace::SubNameSpace::SomeType*> _csharpInstance;

....
}
and a C++ source file containing the class definition
#include "CPlusPlusClass.h"
using namespace TLNameSpace::SubNameSpace;
void CPlusPlusClass::createCSharp()
{
gcroot = new SomeType();
}

void CPlusPlusClass::doSomething()
{
gcroot->someCSharpMethod();
}

.....
In this example, I need the #using <CSharpModule.dll> directive in the C++
header. One way to avoid this is
to split CPlusPlusClass into CPlusPlusInterface and CPlusPlus
Implementation.
A more elegant technique in C++ would be a forward declaration for
TLNameSpace::SubNameSpace::SomeType in
the C++ header. However, I didn't find out how to do this.
The most promising try was

namespace TLNameSpace {
namespace SubNameSpace {
__gcc class SomeType;
}
}

At least the header compiled. On the #using <CSharpModule.dll> line, I got
an 'already defined' error.
Obviously C++ and C# namespaces are just a little bit the same ....

My question is:

- Is there a way to do the forward declaration described above ?
I'd appreciate any hint/solution for this

[Eckart Haug]

Thanx for the quick reply. Your suggestion would mean that I'd have to add a C# reference to any C++ module
that includes the C++ header. There's lots of them and I'd (for the moment) like to have the C++ <-> C#
interface encapsulated in one C++ module.

Vladimir Nesterovsky wrote:

You can add your C# assembly in a project's references thus you may not
import it explicitly.
--
Vladimir Nesterovsky
e-mail: vl******@nesterovsky-bros.com
home: http://www.nesterovsky-bros.com

I'm working with C# objects from managed C++ using the gcroot template.
There'a a C++ header containing the definition of a C++ class:

#using <mscorlib.dll>
#include <vcclr.h>
#using <CSharpModule.dll>

class CPlusPlusClass
{
....

gcroot<TLNameSpace::SubNameSpace::SomeType*> _csharpInstance;

....
}
and a C++ source file containing the class definition
#include "CPlusPlusClass.h"
using namespace TLNameSpace::SubNameSpace;
void CPlusPlusClass::createCSharp()
{
gcroot = new SomeType();
}

void CPlusPlusClass::doSomething()
{
gcroot->someCSharpMethod();
}

.....
In this example, I need the #using <CSharpModule.dll> directive in the C++
header. One way to avoid this is
to split CPlusPlusClass into CPlusPlusInterface and CPlusPlus
Implementation.
A more elegant technique in C++ would be a forward declaration for
TLNameSpace::SubNameSpace::SomeType in
the C++ header. However, I didn't find out how to do this.
The most promising try was

namespace TLNameSpace {
namespace SubNameSpace {
__gcc class SomeType;
}
}

At least the header compiled. On the #using <CSharpModule.dll> line, I got
an 'already defined' error.
Obviously C++ and C# namespaces are just a little bit the same ....

My question is:

- Is there a way to do the forward declaration described above ?
I'd appreciate any hint/solution for this