Trigger an event in C# node from native C++ code

class SimpleCamera
{
private:
    ImagePtr* image
    std::mutex lock;
public:
    void StartGrabing();
    void OnImageGrabbed(ImagePtr* frame); //EventHandler Function
};

void SimpleCamera::OnImageGrabbed(ImagePtr* frame)
{
    mLock.lock();
    image = frame;
    mLock.unlock();
    //Fire the managed/C# event
}

The OnImageGrabbed is event handler function which is called each time frame is available. I am supposed to use this frame to display an image on GUI which is written in C#. However, the restriction from camera vendor is that I cannot access UI objects in this function.

The way I was planning to display an image on C# GUI is that I would like to trigger an event in C# code from within OnImageGrabbed() function(native C++ code) which will in turn access the ImagePtr in C++, copy the data over and display on the C# GUI. I have the copying the data over figured out but not triggering the event.

How can I do this?