C# Observable HTTP

Example.cs

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System.Collections.Immutable;
using System.Linq;
using System.Net.Http;
using System.Reactive;
using System.Reactive.Concurrency;
using System.Reactive.Disposables;
using System.Reactive.Joins;
using System.Reactive.Linq;
using System.Reactive.Subjects;
using System.Reactive.Threading.Tasks;
using System.Web;

class UserService
{
    public UserService(Http http) => this.http = http;

    public IObservable<UserWithAvatar> GetUserWithAvatar(int userId) =>
        from response in http.Get($"api/users/{userId}")
        from user in JsonConvert.DeserializeObject<JObject>(response.Data)
        from avatarResponse in http.Get($"api/avatars/{user["AvatarId"]}")
        from avatar in JsonConvert.DeserializeObject<Avatar>(avatarResponse.Data)
        into avatarStream
        from avatar in avatarStream
        select new UserWithAvatar
        {
            Id = (int)user["Id"],
            Avatar = avatar,
            AvatarId = avatar.Id
        } into x
        from y in x
        select y

    readonly Http http;
}

class Http
{
    public Http(HttpClient http) => this.http = http;
    readonly HttpClient http;

    public IObservable<ObservableHttpResponseMessage> Get(string url) => Observable.FromAsync(async() =>
    {
        var response = await this.http.GetAsync(url);
        var data = await response.Content.ReadAsStringAsync();
        return new ObservableHttpResponseMessage
        {
            Data = data
        };
    });
    public class ObservableHttpResponseMessage
    {
        public string Data { get; set; }
    }
}
static class JsonConvert
{
    public static IObservable<T> DeserializeObject<T>(string value) =>
        Observable.FromAsync(async () =>
        {
            using (var memoryStream = new MemoryStream(value.Select(x => (byte)x).ToArray()))
            using (var streamReader = new StreamReader(memoryStream))
            using (var jsonReader = new JsonTextReader(streamReader))
            {
                return Newtonsoft.Json.JsonConvert.DeserializeObject<T>(await jsonReader.ReadAsStringAsync());
            }
        });
}

class User
{
    public int Id { get; set; }

}
class Avatar
{
    public int Id { get; set; }
}
interface IAvatarBearer
{
    Avatar Avatar { get; set; }
    int Id { get; set; }
}
class UserWithAvatar : User, IAvatarBearer
{
    public Avatar Avatar { get; set; }
    public int AvatarId { get; set; }
}