Code is bypassing await and not stoppping for api to complete [duplicate]

Question

In reference to my previous question,I made the necessary changes but still my code was giving blank data.So ,I created a poc but this is having some issue(blank data as output). I can see json output on browsing 'http://localhost:50193/api/people'

On Debugging,I found below information.

Error in POC; Status=Waiting or activation. Method="null" Result-Not yet Computed.

Also,program is exiting on HttpResponseMessage response = await client.GetAsync("api/people"); so I can not debug further.

Person.cs

using System; namespace CoreTaskApp { public class Person { public int Id { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public DateTime StartDate { get; set; } public int Rating { get; set; } public override string ToString() { return string.Format("{0} {1}", FirstName, LastName); } } }

PersonRepository.cs

using System; using System.Collections.Generic; using System.Net.Http; using System.Net.Http.Headers; using System.Threading; using System.Threading.Tasks; using Newtonsoft.Json; namespace CoreTaskApp { public class PersonRepository { HttpClient client = new HttpClient(); public PersonRepository() { client.BaseAddress = new Uri("http://localhost:50193/"); client.DefaultRequestHeaders.Accept.Add( new MediaTypeWithQualityHeaderValue("application/json")); } public async Task<List<Person>> GetAsync() { await Task.Delay(3000); //cancellationToken.ThrowIfCancellationRequested(); HttpResponseMessage response = await client.GetAsync("api/people"); if (response.IsSuccessStatusCode) { var stringResult = await response.Content.ReadAsStringAsync(); return JsonConvert.DeserializeObject<List<Person>>(stringResult); } return new List<Person>(); } } }

Program.cs

using System; using System.Collections.Generic; using System.Threading; using System.Threading.Tasks; namespace CoreTaskApp { class Program { // private static CancellationTokenSource tokenSource; static void Main(string[] args) { var repository = new PersonRepository(); Task<List<Person>> peopleTask = repository.GetAsync(); peopleTask.ContinueWith(task => { List<Person> people = task.Result; foreach(var person in people) Console.WriteLine(person.ToString()); Environment.Exit(0); }, TaskContinuationOptions.OnlyOnRanToCompletion); } } }

====================================================================== Updated:

static void Main(string[] args) { var repository = new PersonRepository(); Task<List<Person>> peopleTask = repository.GetAsync(); Task<List<Person>> peopleTask1 = repository.GetAsync(); List<Person> people = peopleTask.Result; // or 'await' in an async Main(), C# 7.1 List<Person> people1 = peopleTask1.Result; // or 'await' in an async Main(), C# 7.1 //Add both model to create a single foreach (var person in people) Console.WriteLine(person.ToString()); Console.ReadLine(); }

A Console app is not the best place to test async methods. Put a ReadLine() in the end of Main(), give the task time to complete. — Henk Holterman
– Henk Holterman, Commented Jun 26, 2018 at 17:16
also,I believe I have added await so it should handle the time needed.Appologies I my understanding is wrong — Pooja Malik
– Pooja Malik, Commented Jun 26, 2018 at 17:30

Henk Holterman · Accepted Answer · 2018-09-20 09:30:37Z

Replace your Main with

var repository = new PersonRepository(); Task<List<Person>> peopleTask = repository.GetAsync(); List<Person> people = task.Result; // or 'await' in an async Main(), C# 7.1 foreach(var person in people) Console.WriteLine(person.ToString()); Console.ReadLine();

And maybe wrap it in a try/catch.
The whole ContinueWith is of no use here.

======

Edit, for multiple tasks. As I said a ConsoleApp is not great so fix that first. Makes the rest more suitable for other types of programs:

static void Main() { MainAsync().Wait(); // add some error handling } // option 1, async and sequential static Task MainAsync() { var repository = new PersonRepository(); List<Person> people1 = await repository.GetAsync(); List<Person> people2 = await repository.GetAsync(); // use the results } // option 2, parallel static Task MainAsync() { var repository = new PersonRepository(); Task<List<Person>> peopleTask1 = repository.GetAsync(); Task<List<Person>> peopleTask2 = repository.GetAsync(); await Task.WaitAll(peopleTask1 , peopleTask2); List<Person> people1 = peopleTask1.Result; // should be completed now List<Person> people2 = peopleTask2.Result; // use the results }

Option 2 is better for a small number of CPU intensive tasks. For calling 2 APIs at the same time probaly better too, depending on network.

Option 1 is essential when Tasks depends on each other.

thanks A lot Sir, but can you explain a bit.What hanged as It similar to my solution why mine was not working ?Also,if I need 2 task and want to work after getting result from both the task,can I use my updated answer
For more tasks, use WaitAll(). Not sure what was wrong, or what was the aim, of your CobtinuWith. But just keep it simple, always works better.

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