调用 Async WebClient 方法停止

Question

I have the following piece of code:

public ActionResult DraftScores()
    {
// other code

var json = "";

var fixturesUrl = "someURL";


using (WebClient wc = new WebClient())
{
    wc.Headers.Add("X-Auth-Token", "7d594032xxxxxxxxxxxxxxxxxxxxx");
    json = wc.DownloadString(fixturesUrl);
}

var fixtureList = new JavaScriptSerializer().Deserialize<FixtureList>(json);

model.Matches = fixtureList.matches;

        return View(model);
    }

I tried to extract this into it's own Async method:

    private async Task<List<Match>> GetFixturesAsync()
    {
        var json = "";

        var fixturesUrl = "someURL";

        using (WebClient wc = new WebClient())
        {
            wc.Headers.Add("X-Auth-Token", "7d594032xxxxxxxxxxxxxxxxxxxxx");
            json =  await wc.DownloadStringTaskAsync(fixturesUrl);
        }

        var fixtureList = new JavaScriptSerializer().Deserialize<FixtureList>(json);

        return fixtureList.matches;
    }

calling code:

public ActionResult DraftScores()
    {

//other code

var fixtures = GetFixturesAsync();

   //other code

    model.Matches = fixtures.Result;

        return View(model);
    }

In the original code the call to DownloadString executes in about 200ms. However the call to DownloadStringTaskAsync is still running after several seconds. Is there something wrong with the way that I have written the method?

Answer 1

To do async I/O properly, you need an unbroken await chain from your Controller to the DownloadStringTaskAsync() call.

Step 1, make the Action async.
Step 2, await the async call.

public async Task<ActionResult> DraftScores()
{
   ...
   List<Match> result = await GetFixturesAsync();
   ...
}

Always avoid async void , .Result and .Wait()