Передать string из C# в качестве char* в с++ ClassLibrary

// This is the main DLL file.
 
#include "stdafx.h"
 
#include "HoughTransformator.h"
 
using namespace HoughTransform;
 
int HoughTransformator::Transform(){
    return Transform("scan-1.png", " ");
}
 
int HoughTransformator::Transform(string sourcePath, string targetPath){         
 
    Mat src = imread(sourcePath, 0);
    if(src.empty()) return -1;
    Mat dst, cdst;
    Canny(src, dst, 50, 200, 3);
    cvtColor(dst, cdst, CV_GRAY2BGR);
 
#if 0
    vector<Vec2f> lines;
    HoughLines(dst, lines, 1, CV_PI/180, 100, 0, 0 );
 
    for( size_t i = 0; i < lines.size(); i++ )
    {
        float rho = lines[i][0], theta = lines[i][1];
        Point pt1, pt2;
        double a = cos(theta), b = sin(theta);
        double x0 = a*rho, y0 = b*rho;
        pt1.x = cvRound(x0 + 1000*(-b));
        pt1.y = cvRound(y0 + 1000*(a));
        pt2.x = cvRound(x0 - 1000*(-b));
        pt2.y = cvRound(y0 - 1000*(a));
        line( cdst, pt1, pt2, Scalar(0,0,255), 3, CV_AA);
    }
#else
    vector<Vec4i> lines;
    HoughLinesP(dst, lines, 1, CV_PI/180, 50, 50, 10 );
    for( size_t i = 0; i < lines.size(); i++ )
    {
        Vec4i l = lines[i];
        line( cdst, Point(l[0], l[1]), Point(l[2], l[3]), Scalar(0,0,255), 3, CV_AA);
    }
#endif
    imshow("source", src);
    imshow("detected lines", cdst);
    waitKey();
    return 0;
}

// HoughTransformator.h
#pragma once
#include "opencv2\highgui\highgui.hpp"
#include "opencv2\imgproc\imgproc.hpp"
 
using namespace cv;
using namespace std;
 
using namespace System;
 
namespace HoughTransform {
 
    public ref  class HoughTransformator
    {
    public:
        int Transform(string sourcePath, string targetPath);
        int Transform();
    };
}