Incoming deserialized JSON always NULL

Question

I am working on making a WEB API post that takes in JSON and turns it into a model object so it can be put in the database.

    [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);
    }

However, the docModel is flagging a warning that it will always be null. Why would it be null after deserializing incoming json?

Answer 1

The key thing is this:

    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);
}

If docModel is not null, you return with BadRequest. The place it is flagging it always being null is only reached if the if test is false. I suspect you have the wrong relational operator on your 'if' statement.

Answer 2

在197行上，它始终为null，因为如果不是，它将在if行上进入190行，如果在194行上返回，则如果它不为null则永远不会到达197行。