Howto call an unmanaged C++ function with a std::vector as parameter from C#?

Question

I have a C# front end and a C++ backend for performance reasons. Now I would like to call a C++ function like for example:

void findNeighbors(Point p, std::v         


        

Answer 1

The impedance mismatch is severe. You have to write a wrapper in the C++/CLI language so that you can construct a vector. An additional problem is Point, your C++ declaration for it is not compatible with the managed version of it. Your code ought to resemble this, add it to a class library project from the CLR node.

#include 

using namespace System;
using namespace System::Collections::Generic;

struct Point { int x; int y; };
void findNeighbors(Point p, std::vector &neighbors, double maxDist);

namespace Mumble {

    public ref class Wrapper
    {
    public:
        List^ FindNeigbors(System::Drawing::Point p, double maxDist) {
            std::vector neighbors;
            Point point; point.x = p.X; point.y = p.Y;
            findNeighbors(point, neighbors, maxDist);
            List^ retval = gcnew List();
            for (std::vector::iterator it = neighbors.begin(); it != neighbors.end(); ++it) {
                retval->Add(System::Drawing::Point(it->x, it->y));
            }
            return retval;
        }
    };
}

Do note the cost of copying the collection, this can quickly erase the perf advantage you might get out of writing the algorithm in native C++.