HttpClient GetAsync Fails

Question

I have been experimenting with building a Windows ConsoleApp to be run as a WebService to sync some data back and forth I have built a project for syncing and when I ran it through my wpf project it seemed to work but not it's not.

using System; using System.Collections.Generic; using System.Diagnostics; using System.Net.Http; using System.Net.Http.Headers; using QAQC_DataCommon.Models; namespace TestApp { class Program { static void Main(string[] args) { Gettasks(); } public static async void Gettasks() { using (var client = new HttpClient()) { client.BaseAddress = new Uri("http://localhost/QAQC_SyncWebService/"); client.DefaultRequestHeaders.Accept.Clear(); client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); try { var response = await client.GetAsync("Tasks/?username=XXXXXX&LastUpdated=1/1/15"); if (response.IsSuccessStatusCode) { List<QaqcRow> ls = await response.Content.ReadAsAsync<List<QaqcRow>>(); foreach (QaqcRow qaqcRow in ls) { Debug.WriteLine(qaqcRow.GetValue("BusinessUnit")); } } } catch (Exception) { throw; } } } }

}

It gets up to Var response = Await line when it just exits. No exceptions or any warnings, if I am debugging it just stops.

my output is:

The thread 0x1414 has exited with code 259 (0x103). The thread 0x16e4 has exited with code 259 (0x103). The program '[9656] TestApp.vshost.exe' has exited with code 0 (0x0).

My controller from my webservice is as follows:

public IEnumerable<QaqcRow> Index(string username, string lastUpdated) { return GetFilteredList(username, lastUpdated).OrderBy(x => x.GetValue("FormId")); }

I can manually go to the webservice via the link and i get data, but when i use httpclient it just dies.

Community · Accepted Answer · 2017-05-23 12:31:25Z

It's prematurely exiting the program since it doesn't wait for the end of the execution I guess. (see e.g. https://stackoverflow.com/a/15149840/5296568)

Change

public static async void Gettasks()

To

public static async Task Gettasks()

Then await the end of the execution.

 static async void Main(string[] args) { await Gettasks(); }

Edit: Ahem, so it turns out that Main cannot be async. So maybe for now just confirm that this method get's called properly until the end by blocking the thread.

 static void Main(string[] args) { Gettasks(); Console.ReadLine(); //just don't press enter immedietly :) }

Oops, posted without thinking. You should still be able to wrap it into a Task or something. I added a workaround.
Or you can do Gettasks().Wait(). It is OK to do that in the main method.
thanks, that was it. It looks like i need to brush up on my asyc.

Brendan · Accepted Answer · 2022-05-15 06:03:17Z

Very strange issue, but for me the place I was calling the method that has the http client inside of it was not being awaited:

In my console app I had:

ExampleClass.DoWorkUsingHttpClient()

Changing it to await the method fixed the issue:

await ExampleClass.DoWorkUsingHttpClient()

Additionally my classes were setup like this (sudo code):

public async static ExampleClass { public async static Task DoWorkUsingHttpClient() { var httpClient = new HttpClient(); var result = await httpClient.GetAsync("https://www.example.com"); } }

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