c# - HttpClient PostAsync() never return response

Question

My problem is very similar to this question here. I have an AuthenticationService class that makes an HttpClient PostAsync() and never returns the result when I am running it from the ASP project, but when I implement it in a Console app it works just fine.

This is my Authentication Service class:

public class AuthenticationService : BaseService
{
    public async Task<Token> Authenticate (User user, string url)
    {
        string json = JsonConvert.SerializeObject(user);
        StringContent content = new StringContent(json, Encoding.UTF8, "application/json");

        HttpResponseMessage response = await _client.PostAsync(url, content);
        string responseContent = await response.Content.ReadAsStringAsync();
        Token token = JsonConvert.DeserializeObject<Token>(responseContent);

        return token;
    }
}

And it is here where it hangs: HttpResponseMessage response = await _client.PostAsync(url, content);

Here is my Controller calling the service:

public ActionResult Signin(User user)
{
    // no token needed to be send - we are requesting one
    Token token =  _authenticationService.Authenticate(user, ApiUrls.Signin).Result;
    return View();
}

Here is an example of how I have been testing the service using a Console app, and it runs just fine.

class Program
{
    static void Main()
    {
        AuthenticationService auth = new AuthenticationService();

        User u = new User()
        {
            email = "[email protected]",
            password = "password123"
        };

        Token newToken = auth.Authenticate(u, ApiUrls.Signin).Result;

        Console.Write("Content: " + newToken.user._id);
        Console.Read();
    }
}

Answer 1

Since you are using .Result, this will end up causing a deadlock in your code. The reason this is working in a console application is because console applications don't have contexts, but ASP.NET apps do (see Stephen Cleary's Don't Block on Async Code). You should make the Signin method in your controller async and await the call to _authenticationService.Authenticate to resolve the deadlock issue.