c# - IFormFile 总是在 dotnet core 2.0 上返回 Null 值

Question

我有一个对我的 PhotosController 类的发布请求。当我测试这段代码时，它总是返回一个空值。我没有看到文件详细信息。基本上它获取 userid 和 PhotoDto 并且它应该返回照片。我使用 Cloudinary 服务来存储照片。我的 clodinary API 设置位于 appsettings.json 文件中，这些设置没有问题。当我调试代码时，问题出现在 if (file.Length > 0) 的位置。我猜没有文件。

这是我的 PhotoForCreationDto 文件:

public class PhotoForCreationDto
{
    public string Url { get; set; }
    public IFormFile File { get; set; }
    public string Description { get; set; }
    public DateTime DateAdded { get; set; }
    public string PublicId { get; set; }

    public PhotoForCreationDto()
    {
        DateAdded = DateTime.Now;
    }
}

这是我的 PhotosController 文件:

    [Authorize]
[Route("api/users/{userId}/photos")]
public class PhotosController : Controller
{
    private readonly IDatingRepository _repo;
    private readonly IMapper _mapper;
    private readonly IOptions<CloudinarySettings> _cloudinaryConfig;
    private Cloudinary _cloudinary;

    public PhotosController(IDatingRepository repo,
        IMapper mapper,
        IOptions<CloudinarySettings> cloudinaryConfig)
    {
        _mapper = mapper;
        _repo = repo;
        _cloudinaryConfig = cloudinaryConfig;

        Account acc = new Account(
            _cloudinaryConfig.Value.CloudName,
            _cloudinaryConfig.Value.ApiKey,
            _cloudinaryConfig.Value.ApiSecret
        );

        _cloudinary = new Cloudinary(acc);
    }

    [HttpGet("{id}", Name = "GetPhoto")]
    public async Task<IActionResult> GetPhoto(int id)
    {
        var photoFromRepo = await _repo.GetPhoto(id);

        var photo = _mapper.Map<PhotoForReturnDto>(photoFromRepo);

        return Ok(photo);
    }

    [HttpPost]
    public async Task<IActionResult> AddPhotoForUser(int userId, PhotoForCreationDto photoDto)
    {
        var user = await _repo.GetUser(userId);

        if (user == null)
            return BadRequest("Could not find user");

        var currentUserId = int.Parse(User.FindFirst(ClaimTypes.NameIdentifier).Value);

        if (currentUserId != user.Id)
            return Unauthorized();

        var file = photoDto.File;

        var uploadResult = new ImageUploadResult();

        if (file.Length > 0)
        {
            using (var stream = file.OpenReadStream())
            {
                var uploadParams = new ImageUploadParams()
                {
                    File = new FileDescription(file.Name, stream)
                };

                uploadResult = _cloudinary.Upload(uploadParams);
            }
        }

        photoDto.Url = uploadResult.Uri.ToString();
        photoDto.PublicId = uploadResult.PublicId;

        var photo = _mapper.Map<Photo>(photoDto);

        photo.User = user;

        if (!user.Photos.Any(m => m.IsMain))
            photo.IsMain = true;

        user.Photos.Add(photo);



        if (await _repo.SaveAll())
        {
            var photoToReturn = _mapper.Map<PhotoForReturnDto>(photo);
            return CreatedAtRoute("GetPhoto", new { id = photo.Id }, photoToReturn);
        }

        return BadRequest("Could not add the photo");
    }
}

这是 postman 的错误:

我尝试使用 [FromBody] 但它也没有用。我会 appriciate 任何帮助。

Answer 1

从 Postman 提交文件时，请确保您没有自己填写 Content-Type header 。 Postman 会自动将其设置为 multipart/form-data 值。

将 Content-Type header 设置为 application/json 会阻止 ASP.Net Core 正确处理请求数据。这就是为什么 IFormFile 属性未填充并设置为 null 的原因。