Async method does not return asp.net mvc 4

Question

I'm having a problem with an async method that I implemented. The method basically makes a HttpRequest to a resource and deserializes the string if the request is successful. I wrote a test for the method, and it works. But the method does never return when I call it from a controller?

    public async Task<IEnumerable<T>> Get()
    {
        try
        {
            var resourceSegmentUri = new Uri(_uri, UriKind.Relative);

            var response = await _client.GetAsync(resourceSegmentUri);

            if (response.IsSuccessStatusCode)
            {
                var submission = await response.Content.ReadAsStringAsync();
                return JsonConvert.DeserializeObject<IEnumerable<T>>(submission);
            }

            if (response.Content != null)
            {
                var message = response.Content.ReadAsStringAsync();
                throw new WebException(message.Result, (WebExceptionStatus)response.StatusCode);
            }

        }
        catch (WebException e)
        {
            Logger.Error("GET Request failed with status: {0}", e.Status);
            throw;
        }

        throw new Exception();
    }

Code that never returns:

public ActionResult Index()
{
   var api = new Api();
   var test = api.Get().Result; //Never returns
   return View();
}

Test that works:

[Test]
public void GetShouldReturnIfSuccessfulRequest()
{
    var api = new Api();
    var submission = api.Get();

    Console.WriteLine(JsonConvert.SerializeObject(submission));
    Assert.NotNull(submission);
}

Does anyone know the problem?

Answer 1

You've got a deadlock because you're calling .Result in your controller action.

If you use async/await then you have to use asynchronous actions too.

So something like this should fix it:

public async Task<ActionResult> Index()
{
  var api = new Api();
  var test = await api.Get(); // Should return
}

There's a comprehensive article about this here: Using Asynchronous Methods in ASP.NET MVC 4