upload photo to server vk

//=====================================================================================================================================
        std::string postthis = "";
        postthis += "group_id=111074163&access_token=[ТОКЕН]&v=5.59";
// получаю и вывожу адрес для загрузки фото:
        std::string upload_url = Programm::getWallUploadServer(postthis);
        richTextBox1->Text = gcnew System::String(upload_url.c_str());// вывод результата
// получаю полный путь фотографии
        TCHAR szFileName[MAX_PATH], szPath[MAX_PATH];
        GetModuleFileName(0, szFileName, MAX_PATH);
        Programm::ExtractFilePath(szFileName, szPath);
        strcat(szPath, "1.jpg");
// отправляю фото [(адрес загрузки фото на сервер вк, полный путь фото на диске)]
        std::string res = Programm::UploadPhoto(upload_url, std::string(szPath));
        richTextBox1->Text += "\n\n" + gcnew System::String(res.c_str());// вывод результата

//=====================================================================================================================================
// класс Programm:
std::string Programm::getWallUploadServer(std::string fields)
{
    std::string content;
    char temp[50];
    CURL *curl = curl_easy_init();
    if (curl)
    {

        //----------------------------------------------------------------------------------------
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
        curl_easy_setopt(curl, CURLOPT_URL, "https://api.vk.com/method/photos.getWallUploadServer.xml?");
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, fields.c_str());
        curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)fields.size());

        //  сохраняем html код cтраницы в строку content
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &content);
        // Загловок ответа сервера выводим в консоль
        //      curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, write_head);
        //      curl_easy_setopt(curl, CURLOPT_WRITEHEADER, &std::cout);

        CURLcode res = curl_easy_perform(curl);
        if (res != CURLE_OK)
        {
            sprintf(temp, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res)); //  fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
            return std::string(temp);
        }
    //  return content;
        curl_easy_cleanup(curl);
    }
    // парсинг ссылки:
    XML::XMLDocument xml;
    xml.Parse(content.c_str());
    if (xml.FirstChildElement("response")->FirstChildElement("upload_url") != nullptr)
    {
        return content = std::string(xml.FirstChildElement("response")->FirstChildElement("upload_url")->GetText());
    }
    else return content = "error parse";
}

std::string Programm::UploadPhoto(std::string upload_url, std::string file)
{
    std::string content, fields = "photo" + file;
    String^ managed = msclr::interop::marshal_as<String^>(file.c_str());
    if (!File::Exists(managed)) { return content = "no_photo"; }

//----------------------------------------------------------
    CURL* curl;
    char buff[200];
    struct curl_httppost* post = NULL;
    struct curl_httppost* last = NULL;

    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();
    curl_formadd(&post, &last, CURLFORM_COPYNAME, "photo", CURLFORM_FILE, file.c_str(), CURLFORM_CONTENTTYPE, "multipart/form-data", CURLFORM_END);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
    curl_easy_setopt(curl, CURLOPT_URL, upload_url.c_str());
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, fields.c_str());
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)fields.size());
//  curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
//  curl_easy_setopt(curl, CURLOPT_HEADER, 1);
//  curl_easy_setopt(curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1");
//  curl_easy_setopt(curl, CURLOPT_HTTPPOST, post);

//  сохраняем html код cтраницы в строку content
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &content);

    CURLcode res = curl_easy_perform(curl);

    if (res != CURLE_OK)
    {
        sprintf(buff, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res)); //  fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        return std::string(buff);
    }
//  else { return content = "res == CURLE_OK"; }
    return content;
    curl_easy_cleanup(curl);
}