Async JSON deserialisation in ASP.NET

Question

I have a small MVC 5 application that calls a web service, and receives a JSON response. I deserialise the response into my own type and it gets passed on to the view and data is displayed by razor.

The controller handler:

    public async Task<ActionResult> Search(string q)
    {
        var vm = new SearchResultViewModel(await _searchService.GetDataAsync(q));
        return View(vm);
    }

The search service method:

    public async Task<ISearchResult> GetDataAsync(string q)
    {
        var fullRequest = new UriBuilder(RequestUri) {Query = "q=" + q};

        var result = await _client.GetAsync(fullRequest.ToString()).ConfigureAwait(false);

        if (result.IsSuccessStatusCode)
        {
            var jsonResponse = await result.Content.ReadAsStringAsync().ConfigureAwait(false);

            // How should I call this?
            return JsonConvert.DeserializeObject<SearchResult>(jsonResponse);
        }
        return new SearchResult
    }

My question: How should I call JsonConvert.DeserializeObject? It's an inherently CPU bound operation, so is it ok to call synchronously (and block the thread) since I can't return until it's done anyway? If there's a problem with deserialisation, a cancellation token couldn't be used.

If I should call asynchronously, should I use Task.Factory.StartNew() as suggested by intellisense, as a replacement for the deprecated JsonConvert.DeserializeObjectAsync()? This Channel 9 video suggests (at 58mins) that this isn't such a good idea. Perhaps another option, such as Task.Run()? Possibly a bad idea since it might cause SyncContext issues?

Any pointers gratefully received!

I don't think there is any difference between Task.Factory.StartNew() and Task.Run() except if you don't want to use the threadpool. I would say your code is fine as is (eg deserialize synchronously) unless the JSON is likely to be large in which case you could do a buffered data read from your result.Content as a stream (if possible) and deserialize the JSON in a streaming manner rather than allocating the entire string first. — jamespconnor
– jamespconnor, Commented Mar 12, 2016 at 23:33
@SimonB: For future reference, do not use Task.Factory.StartNew; it has dangerous defaults. Task.Run is safer. However, in most cases, neither should be used on ASP.NET. — Stephen Cleary
– Stephen Cleary, Commented Mar 14, 2016 at 15:52
@StephenCleary Thanks for the heads up! I'm not sure what the use cases are for ASP.NET, particularly for CPU-bound ops. Perhaps if you have some parallel tasks to run? Obviously high parallelism has its own issues in a web server context. — Simon B
– Simon B, Commented Mar 15, 2016 at 23:39
@SimonB: CPU-bound code should just be run directly on ASP.NET. I do not recommend any parallelism in web apps. — Stephen Cleary
– Stephen Cleary, Commented Mar 16, 2016 at 11:22

Yacoub Massad · Accepted Answer · 2016-03-12 23:35:39Z

3

Your code is good as is. DeserializeObject will run inside a thread-pool thread since you are using ConfigureAwait(false).

Your overall method (GetDataAsync) would still be asynchronous since it will return to the caller on the first await.

edited Mar 12, 2016 at 23:35

answered Mar 12, 2016 at 23:33

Yacoub Massad

27.9k2 gold badges42 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Alexei Levenkov Over a year ago

Side note: question marked with ASP.Net where using ConfigureAwait(false) does not do any good (using it is generally cargo cult programming). It also actively harmful if code after the async call needs access to request or current culture (see stackoverflow.com/questions/13489065/… for long discussion)

Collectives™ on Stack Overflow

Async JSON deserialisation in ASP.NET

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related