Thread: Using C++ classes in C# with C++/CLI

1. Constructor and Destructor

Code:

//.h
    public ref class WrapperLibrary
    {
    public:
        WrapperLibrary();
        !WrapperLibrary();
        ~WrapperLibrary();
 
    internal: 
        CCppLibrary *u_cppLibrary;
    };

Code:

//.cpp
    WrapperLibrary::WrapperLibrary()
    {
        u_cppLibrary = new CCppLibrary();
    }
 
    WrapperLibrary::!WrapperLibrary()
    {
        delete u_cppLibrary;
    }
 
    WrapperLibrary::~WrapperLibrary()
    {
        this->!WrapperLibrary();
    }

2. Inheritance

Code:

//.h
    public ref class WrapperLibrary
    {
 
        // ...
 
    internal:
        WrapperLibrary(CCppLibrary *u_cppLibrary);
        CCppLibrary *u_cppLibrary;
    };
 
    public ref class ChildWrapper : WrapperLibrary
    {
    public:
        ChildWrapper();
    };

Code:

//.cpp
    WrapperLibrary::WrapperLibrary(CCppLibrary *u_cppLibrary)
    {
        this->u_cppLibrary = u_cppLibrary;
    }
 
    ChildWrapper::ChildWrapper()
        : WrapperLibrary(new CChildCpp())
    {
    }

3. String Argument

Code:

//.cpp
    String ^WrapperLibrary::AppendHello(String ^str)
    {
        msclr::interop::marshal_context context;
 
 
        const char *u_str = context.marshal_as<const char *>(str);
 
 
        std::string result = u_cppLibrary->AppendHello(u_str);
 
 
        String ^ret = context.marshal_as<String  ^>(result);
 
 
        return ret;
    }

4. Function Pointer Argument

Code:

//.h
 
    // ...
 
    using namespace System::Runtime::InteropServices;
 
    // ...
 
    [UnmanagedFunctionPointerAttribute(CallingConvention::Cdecl)]
    public delegate void Callable();
 
    // ...
 
    public ref class WrapperLibrary
    {
        // ...
 
    public:
  
        void Call(Callable ^callable);
  
        // ...
    };

Code:

//.cpp
    void WrapperLibrary::Call(Callable ^callable)
    {
        void (*u_callable)() = callable == nullptr ? NULL : (void (*)()) Marshal::GetFunctionPointerForDelegate(callable).ToPointer();
  
        u_cppLibrary->Call(u_callable);
    }

5. Variable Argument Function

Code:

//.cpp
 
struct FakeValist
{
    // NOTE : the number of arguments is limited
    static const int COUNT = 100;
    double list[COUNT];
};
 
 
void GetNumbers(FakeValist *fakeValist, ...array<double> ^numbers)
{
    int count = numbers->GetLength(0);
 
 
    for (int i = 0; i < count; i++)
    {
        fakeValist->list[i] = numbers[i];
    }
}
 
// ...
 
    double WrapperLibrary::Average(...array<double> ^numbers)
    {
        int count = numbers->GetLength(0);
        FakeValist u_numbers;
        GetNumbers(&u_numbers, numbers);
 
        double ret = u_cppLibrary->Average(count, u_numbers);
 
        return ret;
    }

5-1. Variable Argument Function ( String Formatting )

Code:

//.cpp
    void WrapperLibrary::Printf(String ^format, ...array<Object ^> ^args)
    {
        msclr::interop::marshal_context context;
 
        String ^formatted = String::Format(format, args);
        const char *u_formatted = context.marshal_as<const char *>(formatted);
 
        u_cppLibrary->Printf("%s", u_formatted);
    }

6. Export Unmanaged Member

Code:

//.h
 
//...
 
class CCppLibrary;
#pragma make_public(CCppLibrary)
 
//...
    public ref class WrapperLibrary
    {
        //...
 
    public:
​        WrapperLibrary(CCppLibrary *u_cppLibrary);    // Used in OtherCliLibrary. Turned private if 'make_public' not exist
 
    //...