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POHow to override a C++ virtual method (not in an interface class) in C# via C++/CLI
 

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  1. POHow to override a C++ virtual method (not in an interface class) in C# via C++/CLI
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    <p>For reference, this question deals with accessing the C++ NaturalPoint Camera SDK via C#.</p> <p>I am trying to pass along the implementation of a virtual method from C++ to C#. The trouble I am having is that the C++ virtual method is not in an interface class and I am not able to change that. Here is the class declaration:</p> <pre><code>class CLAPI cCameraListener { public: cCameraListener() {}; ~cCameraListener() {}; virtual void FrameAvailable(); virtual void FrameOverflow(); virtual void ButtonPressed(); }; </code></pre> <p>The CLAPI is defined as:</p> <pre><code>#define CLAPI __declspec(dllexport) </code></pre> <p>I can't inherit from the cCameraListener class in a ref class since it isn't an interface class and haven't come up with any way to expose the virtual methods to a managed class. I also need to be able to register the listener which I talk about more below.</p> <p>Here is the working C++ implementation for listening for frames:</p> <pre><code>// process frames as they arrive class FrameListener: public cCameraListener { public: Camera *myCamera; FrameListener(Camera *cameraPtr) { myCamera = cameraPtr; }; void FrameAvailable() { Frame *thisFrame = myCamera-&gt;GetFrame(); // do something with the frame here thisFrame-&gt;Release(); }; }; int _tmain(int argc, _TCHAR* argv[]) { // startup camera CameraManager::X().WaitForInitialization(); Camera *camera = CameraManager::X().GetCamera(); if(camera==0) { // print an error return 1; } // set camera properties camera-&gt;SendEmptyFrames(false); camera-&gt;SendInvalidFrames(false); camera-&gt;SetVideoType(SegmentMode); // setup frame listener FrameListener *myListener = new FrameListener(camera); camera-&gt;AttachListener(myListener); // start the camera camera-&gt;Start(); // while loop holding thread // clean up camera-&gt;Release(); CameraManager::X().Shutdown(); return 0; } </code></pre> <p>Here is some of the existing C++/CLI wrapper code: Link: <a href="https://code.google.com/p/npcamerasdkdotnet/" rel="nofollow">https://code.google.com/p/npcamerasdkdotnet/</a></p> <pre><code>public ref class MCamera{ public: MCamera(Camera * camera){ this-&gt;camera = camera; } ~MCamera(){ delete this-&gt;camera; } void Start(){camera-&gt;Start();} void SetExposure(int Value){camera-&gt;SetExposure(Value);} void SetThreshold(int Value){camera-&gt;SetThreshold(Value);} void SetIntensity(int Value){camera-&gt;SetIntensity(Value);} // TODO - WRAP THESE METHODS //void AttachListener(cCameraListener * Listener); //void RemoveListener(cCameraListener * Listener); // other wrapped methods here... private: Camera * camera; }; </code></pre> <p>Notice that within the MCamera wrapper class, the AttachListener method needs to be implemented and requires a pointer to the cCameraListener class talked about above.</p> <p>Any suggestions would be appreciated! Thanks!</p>
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    1. COpossible duplicate of [c++/cli pass (managed) delegate to unmanaged code](http://stackoverflow.com/questions/2972452/c-cli-pass-managed-delegate-to-unmanaged-code)
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    2. CO@Hans: That other question doesn't have anything to do with inheritance or virtual methods, that I can see.
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