How to import and use a unmanaged C++ class from C#?
I have an native C++ dll, some header files and the import library. Is the开发者_JAVA百科re a way how to instantiate an object within C# that is defined in the dll?
The two ways I'm aware of are:
- to wrap the C++ code into COM
- to use DLLImport and external C functions
C++/CLI is your friend for this. You'll run into one problem though: it is not possible to store standard C++ objects inside C++/CLI ref or value classes (the ones for .NET). So you'll have to resort to the following class (that you can modify) that I use in production code:
#pragma once
#include <boost/shared_ptr.hpp>
template <typename T>
ref class Handle
{
boost::shared_ptr<T>* t;
!Handle()
{
if (t != nullptr)
{
delete t;
t = nullptr;
}
}
~Handle() { this->!Handle(); }
public:
Handle() : t(new boost::shared_ptr<T>((T*)0)) {}
Handle% operator=(T* p)
{
if (p != t->get()) t->reset(p);
return *this;
}
static T* operator&(Handle% h) { return h.t->get(); }
static boost::shared_ptr<T> operator->(Handle% h) { return *h.t; }
T& reference() { return *t->get(); }
T const& const_reference() { return *t->get(); }
};
Usage: Handle<MyCppClass>^ handle;
inside a C++/CLI class. You then implement stub methods, forwarding them to the handle
member. Garbage collected objects will call destructors of the C++ class instance iff there is no more pointer to it:
public ref class Foo
{
void bar() { handle->bar(); }
internal:
Handle<CppNamespace::Foo>^ handle;
};
I think that your option is only build a C++/CLI class wrapper (so you can reference it like a c# class), otherwise you can't instantiate a c++ class (unmanaged) from c# code.
Alternative could be the "ugly" way: instantiate the c++ class through a c function, but you'll treat the class as a void pointer inside the c# code, so you basically will not do anything with it (except if you create other functions to interact with this class; only C functions)
C# understands C, if you want make it understand C++ you have to use C++/CLI
P.S. C# has some basic understanding of C++ classes, but it's only about converting class data (I mean bytes: fields) into some usable data in C# (there are some Attributes), but will not allow to work with methods and things like that (avoid totally is my suggestion).
精彩评论