// Review the code below written in C# that queries an external API and returns a list of unique IDs returned from that API,

// logging the successful call asynchronously.

// The external API returns a list of non-unique IDs in JSON so we have to make this list unique.

// What can be improved in that code? Are there any antipatterns that can be fixed? Please rewrite it in the best way you can.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Net.Http;

using System.Text.Json;

using System.Threading;

using System.Threading.Tasks;

using Microsoft.Extensions.Logging;

// ...

public static class Program

{

    public static async Task Main(string[] args)

    {

        Utils.list_unique(default(CancellationToken), null);

        foreach (var id in Utils.list_of_unique_ids)

        {

            Console.WriteLine(id);

        }

    }

}

​

public static class Utils

{

    public static List<int> list_of_unique_ids;

    public static async void list_unique(CancellationToken tkn, ILogger logger)

    {

        HttpClient client = new HttpClient();

        var jsonStream = client.GetAsync("https://jsonplaceholder.typicode.com/posts").Result.Content.ReadAsStreamAsync().Result;

        var Posts = JsonSerializer.DeserializeAsync<PostDto[]>(jsonStream).Result;

        list_of_unique_ids = new List<int>();

        foreach (var p in Posts)

        {

            if (list_of_unique_ids.Contains(p.userId))

            {

                continue;

            }

            list_of_unique_ids.Add(p.userId);

        }

        log_async(logger, list_of_unique_ids);

    }

    private static async void log_async(ILogger logger, List<int> IDs)

    {

        await Task.Run(() => logger.LogDebug($"API call succeeded. IDs: {IDs}"));

    }

}

​

public class PostDto

{

    public int userId { get; set; }

    public int id { get; set; }

}