Entity Framework hangs when using async calls

Question

I am new to using async and this seems to elude me on what the cause or issue is, when I attempt to load the webpage the async call seems to hang and the page is never loaded. Is my implementation wrong here?

CONTROLLER

public ActionResult Index()
{

    var model = _partyAddOnService.Get().Result.Select(x => new AddOnModel()
    {
        Id = x.Id,
        AddOnType = x.AddOnType,
        Description = x.Description,
        Name = x.Name,
        Price = x.Price
    });

    return View(model);
}

SERVICE

public async Task<IEnumerable<AddOn>> Get()
{
    return await _repository.GetAsync();
}

REPOSITORY

public async Task<IEnumerable<T>> GetAsync()
{
    return await Context.Set<T>().ToListAsync();
}

UPDATE:

I tried this as well and it still hangs...

public ActionResult Index()
{

    var model = _partyAddOnService.Get();
    return View();
}

* When debugging and looking at the Task status it says "Waiting for activation"

Also tried using the ConfigureAwait method as the article suggested. (see James comment below)

public async Task<IEnumerable<AddOn>> Get()
{
    return await _repository.GetAsync().ConfigureAwait(false);
}

Why are you using async if you want to synchronously obtain the result of the call? Result blocks. — usr
– usr, Commented Jun 18, 2014 at 15:07
I imagine the deadlocking is my controller? Not sure how to fix though. — devfunkd
– devfunkd, Commented Jun 18, 2014 at 15:10
@usr yeah the more I've been reading about it the more I realize this whole thing is a waste of time and effort. I'll remove it and simply just call the database synchronously. I don't have any methods that rely on multiple calls to the database, EF returns my data with children based on FK automatically so I don't need to call multiple times. I was just trying to be proactive in my code architecture. Darn over-eager junior developer syndrome. Thanks for the help (everyone) — devfunkd
– devfunkd, Commented Jun 18, 2014 at 15:53

Stephen Cleary · Accepted Answer · 2014-06-19 01:35:08Z

7

To prevent deadlocks, just use async all the way up. You're already using it in your service and repository, so just add it to your controller:

public async Task<ActionResult> Index()
{
  var model = (await _partyAddOnService.Get()).Select(x => new AddOnModel()
  {
    Id = x.Id,
    AddOnType = x.AddOnType,
    Description = x.Description,
    Name = x.Name,
    Price = x.Price
  });

  return View(model);
}

I also recommend that you change your async methods to end in Async, to follow the Task-based Asynchronous Pattern. I.e., Get should be GetAsync.

answered Jun 19, 2014 at 1:35

Stephen Cleary

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Comments

Edwin van Vliet · Accepted Answer · 2014-06-18 15:22:11Z

1

You are causing a deadlock, because you didn't implement the async-await pattern all the way up. Also use .ConfigureAwait(false) on the lowest level.

public async Task<ActionResult> Index()
{

    var model = await _partyAddOnService.Get().Result.Select(x => new AddOnModel()
    {
        Id = x.Id,
        AddOnType = x.AddOnType,
        Description = x.Description,
        Name = x.Name,
        Price = x.Price
    });

    return View(model);
}

answered Jun 18, 2014 at 15:22

Edwin van Vliet

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2 Comments

devfunkd Over a year ago

Why did this get downvoted? As someone who is trying to learn and understand async I am curious to know if there is something perhaps if I should know something not to do here?

usr Over a year ago

Using async IO and then blocking defeats the point and gets you the worst of both worlds. @yycdev for that reason your own code doesn't make sense either.

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