template<typename T, typename C>
typename std::enable_if<!std::is_convertible<T, std::wstring>::value, typename std::decay<T>::type>::type get_param(const std::wstring& name, C&& params, T fail_value = T())
template<typename T, typename C>
typename std::enable_if<!std::is_convertible<T, std::wstring>::value, typename std::decay<T>::type>::type get_param(const std::wstring& name, C&& params, T fail_value = T())