传入的反序列化JSON始终为NULL

Question

我正在制作一个接收JSON的WEB API帖子，并将其转换为模型对象，以便将其放入数据库中。

    [HttpPost]
    [Route]
    [SwaggerResponse(HttpStatusCode.Created, CreatedMessage)]
    [SwaggerResponse(HttpStatusCode.BadRequest, BadRequestMessage, typeof(HttpError))]
    [SwaggerResponse(HttpStatusCode.Unauthorized, UnauthorizedMessage, typeof(HttpError))]
    [SwaggerResponse(HttpStatusCode.InternalServerError, UnknownErrorMessage, typeof(HttpError))]
    public async Threading.Task<IHttpActionResult> PostDocument([FromBody] Api.Document documentModel)
    {
        // Check if the request contains multipart/form-data.
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }

        // Put the files in a temporary location
        // so then we can ReadAsMultiPartAsync and get access to the other data submitted
        var tempPath = HttpContext.Current.Server.MapPath("~/App_Data/Temp/" + Guid.NewGuid());
        Directory.CreateDirectory(tempPath);

        var deserializer = new DataContractJsonSerializer(typeof(Api.Document));
        HttpContext.Current.Request.InputStream.Position = 0;
        Api.Document docModel = (Api.Document)deserializer.ReadObject(HttpContext.Current.Request.InputStream);

        if (docModel != null)
        {
            // We don't have the json data so delete the TempFiles and return BadRequest
            Directory.Delete(tempPath, true);
            return ResponseMessage(Request.CreateResponse(HttpStatusCode.BadRequest));
        }

        return await PostOrStatusCodeAsync(docModel, RouteNames.GetById).ConfigureAwait(true);
    }

然而，docModel正在标记一个警告，它始终为null。为什么在反序列化传入的json后它会为null？

Answer 1

关键是：

    if (docModel != null)
    {
        // We don't have the json data so delete the TempFiles and return BadRequest
        Directory.Delete(tempPath, true);
        return ResponseMessage(Request.CreateResponse(HttpStatusCode.BadRequest));
    }

    return await PostOrStatusCodeAsync(docModel, RouteNames.GetById).ConfigureAwait(true);
}

如果docModel不为null，则返回BadRequest。只有if测试为false时，才会标记它始终为null的标记位置。我怀疑你的'if'语句中有错误的关系运算符。

Answer 2

在第197行，它将始终为空，因为如果它不是，它将在第190行返回的第01行返回，因此如果它不为空则永远不会到达第197行。