Catalog ids from Registration

program.cs

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;

namespace ConsoleApp3
{
    static class HttpContentExtensions
    {
        public static async Task<JObject> ReadAsJObjectAsync(this HttpContent content)
            => JObject.Parse(await content.ReadAsStringAsync());

        public static async Task<JObject> ReadAsGZippedJObjectAsync(this HttpContent content)
        {
            using var gzipStream = new GZipStream(await content.ReadAsStreamAsync(), CompressionMode.Decompress, leaveOpen: true);
            using var sr = new StreamReader(gzipStream);
            using var jsonTextReader = new JsonTextReader(sr);

            return await JObject.LoadAsync(jsonTextReader);
        }
    }

    class Program
    {
        static async Task Main(string[] args)
        {
            var serviceIndex = "https://api.nuget.org/v3/index.json";
            var packageId = "mysqlconnector";
            //var packageId = "dotnet-depends";
            var registrationResource = "RegistrationsBaseUrl/3.6.0";

            using (var client = new HttpClient())
            {
                var response = await client.GetAsync(serviceIndex);
                response.EnsureSuccessStatusCode();

                var services = await response.Content.ReadAsJObjectAsync();

                var registrationBaseUrl = (string)services.SelectToken($"$['resources'][?(@['@type'] == '{registrationResource}')]['@id']");
                var registrationUrl = $"{registrationBaseUrl}{packageId.ToLower()}/index.json";

                response = await client.GetAsync(registrationUrl);
                response.EnsureSuccessStatusCode();

                var registrationIndex = await response.Content.ReadAsGZippedJObjectAsync();

                // Check if we can get everything from the index
                var catalogEntries = registrationIndex.SelectTokens("$['items'][*]['items'][*]['catalogEntry']['@id']");

                if (catalogEntries.Any())
                {
                    foreach(var catalogEntry in catalogEntries)
                    {
                        Console.WriteLine(catalogEntry);
                    }
                }
                else // There are so many registrations, that it is split into multiple pages.
                {
                    var registrationPages = registrationIndex.SelectTokens("$['items'][*]['@id']");

                    foreach (var registrationPage in registrationPages)
                    {
                        response = await client.GetAsync((string)registrationPage);
                        response.EnsureSuccessStatusCode();

                        var registration = await response.Content.ReadAsGZippedJObjectAsync();

                        catalogEntries = registration.SelectTokens("$['items'][*]['catalogEntry']['@id']");

                        foreach (var catalogEntry in catalogEntries)
                        {
                            Console.WriteLine(catalogEntry);
                        }
                    }
                }
            }
        }
    }
}