public class HWIL_PluginInterface{

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate int set_camera_rate_abs_t(uint cameraID, float yaw, float pitch, float roll);	
}

public struct plugin_interface {

	public HWIL_PluginInterface.set_camera_rate_abs_t set_camera_rate_abs;

	public void RegistryCallback(PluginCallback pluginCallback)
	{
		set_camera_rate_abs += pluginCallback.camera_rate_abs;
	}	
}

public class PluginCallback{

	public int camera_rate_abs(uint cameraID, float yaw, float pitch, float roll)
        {            
            m_log.Debug("camera_rate: CameraId = " + cameraID + ", yaw = " + yaw.ToString() + ", pitch = " + pitch + ", roll = " + roll);
			
			
            return 0;
        }		
}

public int main(){

    [UnmanagedFunctionPointer(System.Runtime.InteropServices.CallingConvention.Cdecl) ]        
    internal delegate HWIL_PluginInterface.result_enum PluginDelegate( MarshalAs(UnmanagedType.Struct)]
                                                                       ref plugin_interface pluginInterface,
                                                                       char[] cf_path,
                                                                       IntPtr usr);

     plugin_interface plugin = new plugin_interface();
     PluginCallback pluginCallback = new PluginCallback();
	
     plugin.RegistryCallback(pluginCallback):
	
     IntPtr m_pluginProc = GetProcAddress(plugin, "load_plugin");
		
     var loadPlugin = (PluginDelegate)Marshal.GetDelegateForFunctionPointer(m_pluginProc, typeof(PluginDelegate));

     loadPlugin(ref plugin, null, IntPtr.Zero);	
}

.h
typedef int(*set_camera_rate_abs_t) (unsigned int cameraID, float yaw, float pitch, float roll);

typedef struct{
   set_camera_rate_abs_t 
        set_camera_rate_abs;
}


.cpp
class PluginAdapter
{
	plugin_interface* m_interface;
	public:
	PluginAdapter(plugin_interface* ptr)
		: m_interface(ptr)
	{
	}

	~PluginAdapter()
	{	
	}

	void load()
	{
		printf("Proxy.Plugin: call camera_state_callback\n");	
		printf("load_plugin: m_interface %d\n", m_interface);
		printf("load_plugin: m_interface->set_camera_rate_abs: %d\n", (long)m_interface->set_camera_rate_abs);
		printf("load_plugin: Proxy.Plugin: Make first call to CAMERA_MODE_RATE\n");

		m_interface->set_camera_rate_abs(0, 5.2, 2.7, 0.2);
		m_thread = new boost::thread( boost::bind(&PluginAdapter::RunCommand, this));

		boost::this_thread::sleep(boost::posix_time::milliseconds(3000));
	}

	void RunCommand()
	{		
		printf("RunCommand: pluginPtr: %d\n", (long)m_interface);
		printf("RunCommand: pluginPtr->set_camera_rate_abs: %d\n", (long)m_interface->set_camera_rate_abs);

		while(true)
		{
			printf("RunCommand: pluginPtr: %d\n", (long)m_interface);
			printf("RunCommand: pluginPtr->set_camera_rate_abs: %d\n\n", (long)m_interface->set_camera_rate_abs);
			
			//m_interface->set_camera_rate_abs(0, 5.0, 20.5, 10.7);
			boost::this_thread::sleep(boost::posix_time::milliseconds(1000));
		}
	}

private:
	boost::thread* m_thread;
};

PluginAdapter* g_plugin;

extern "C" __declspec(dllexport) int load_plugin(plugin_interface *ptr_interface, const char *cf_path, void *usr) 
{	
	g_plugin = new PluginAdapter(ptr_interface);
	g_plugin->load();
	
        printf("load_plugin: ptr_interface->set_camera_rate_abs: %d\n\n", (long)ptr_interface->set_camera_rate_abs);
	boost::this_thread::sleep(boost::posix_time::milliseconds(5000));
	printf("Proxy.Exit\n");
	return RESULT_OK;
}

extern "C" __declspec(dllexport) int load_plugin(plugin_interface *ptr_interface, const char *cf_path, void *usr) 
{	
        plugin_interface *m_interface = new plugin_interface();
        m_interface->set_camera_rate_abs = ptr_interface->set_camera_rate_abs;

	g_plugin = new PluginAdapter(m_interface);
	g_plugin->load();
	
	printf("Proxy.Exit\n");
	return RESULT_OK;
}