在按照课程代码修改并运行后，访问api发生错误
以下是我的代码，controller文件中

        public IActionResult PartiallyUpdateTouristRoute(
        [FromRoute] Guid touristRouteId,
        [FromBody] JsonPatchDocument<TouristRouteForUpdateDto> patchDocument
        )
        {
            if (!_touristRouteRepository.TouristRouteExists(touristRouteId))
            {
                return NotFound("旅游路线找不到");
            }
            //取到数据
            var touristRouteFromRepo = _touristRouteRepository.GetTouristRoute(touristRouteId);
            //打补丁
            var touristRouteToPatch = _mapper.Map<TouristRouteForUpdateDto>(touristRouteFromRepo);
            patchDocument.ApplyTo(touristRouteToPatch);

            _mapper.Map(touristRouteToPatch, touristRouteFromRepo);
            _touristRouteRepository.Save();

            return NoContent();
        }

TouristRouteProfile文件中

        public TouristRouteProfile()
        {
            CreateMap<TouristRoute, TouristRouteDto>()
                .ForMember(
                dest => dest.Price,
                opt => opt.MapFrom(src => src.OriginalPrice * (decimal)(src.DiscountPresent ?? 1))
                )
                .ForMember(
                dest => dest.TravelDays,
                opt => opt.MapFrom(src => src.TravelDays.ToString())
                )
                .ForMember(
                dest => dest.TripType,
                opt => opt.MapFrom(src => src.TripType.ToString())
                )
                .ForMember(
                dest => dest.DepartureCity,
                opt => opt.MapFrom(src => src.DepartureCity.ToString())
                );
            //处理创建资源时的dto
            CreateMap<TouristRouteForCreationDto, TouristRoute>()
                .ForMember(
                    dest => dest.Id,
                    opt => opt.MapFrom(src => Guid.NewGuid())
                );

            CreateMap<TouristRouteForUpdateDto, TouristRoute>();

            CreateMap<TouristRoute, TouristRouteForUpdateDto>();
        }

TouristRoutePictureProfile文件中

    public class TouristRoutePictureProfile:Profile
    {
        public TouristRoutePictureProfile()
        {
            CreateMap<TouristRoutePicture, TouristRoutePictureDto>();
            CreateMap<TouristRoutePictureForCreationDto, TouristRoutePicture>();
            CreateMap<TouristRoutePicture, TouristRoutePictureForCreationDto>();
        }
    }

感谢老师的解答