Program exits while calling await function

Hello, I want to consume REST api. I use code like this:

namespace test2
{

class Program
{
    static void Main(string[] args)
    {
        TestRest t = new TestRest();
        t.Run();
    }
}

public class TestRest
{
    public TestRest() { }

    public async void Run()
    {
        HttpClient client = new HttpClient();
        client.BaseAddress = new Uri("https://community-league-of-legends.p.mashape.com/");
        client.DefaultRequestHeaders.Add("X-Mashape-Authorization", "tcsgoutBcXP5Lu5L2jYBOu4qeXehseiH");
        HttpResponseMessage response = await client.GetAsync("api/v1.0/euw/summoner/getSummonerByName/NICK_FROM_GAME");

        JObject response2 = JsonConvert.DeserializeObject(await response.Content.ReadAsStringAsync()) as JObject;

        foreach (KeyValuePair<string, JToken> j in response2)
        {
            Console.WriteLine("Key:{0} Value:{1}", j.Key, j.Value);
        }
    }
}

}

But while calling method:

await client.getAsync("...

program is exiting. Please help me, its simple console app to consume simple api and i can not manage this :(

Thanks

Jon Skeet
people
quotationmark

There are two problems here:

  • You've got a void async method, which is almost always a bad idea unless it's meant to be an event handler. You should generally make an async method return Task where you'd normally write a void synchronous method.
  • Your app is exiting because there are no foreground threads left running. There'll be a continuation which would fire if the response returned while the process was still alive - but nothing to keep the process alive.

The simplest fix is to address both at the same time - just make the async method return Task, and then use:

static void Main(string[] args)
{
    TestRest t = new TestRest();
    t.Run().Wait();
}

Note that that would be a really bad idea in a WinForms app, as waiting on a Task in the UI thread would basically cause a deadlock. However, in a console app there's no equivalent of the UI thread, so task continuations are scheduled on the thread pool - your "main" thread will block, the continuation in your async method will run on a thread pool thread, and then when that's completed the task that the main thread is waiting for will complete.

people

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