using System;

using System.Collections.Generic;

using System.Globalization;

using System.Text.Json;

using static Converter.UrlDownloaderConverter;

​

CultureInfo.CurrentCulture = new CultureInfo("de-DE", false);

​

const string input = @"

[

    {

        ""title"": ""AAA"",

        ""dates"": [

            {

                ""a_date"": ""24.09.2021"",              

                ""push"": false,

                ""date_url"": ""https://www-api.aaa.com/api/HEUFCCEWJHB=.json""

            },

            {

                ""a_date"": ""27.09.2021"",              

                ""push"": false,

                ""date_url"": ""https://www-api.aaa.com/api/VFEWVWEWXS=.json""

            }

        ]

    },

    {

        ""title"": ""BBB"",

        ""dates"": [

            {

                ""a_date"": ""24.10.2021"",              

                ""push"": false,

                ""date_url"": ""https://www-api.aaa.com/api/HBTFDECEC=.json""

            },

            {

                ""a_date"": ""27.10.2021"",              

                ""push"": false,

                ""date_url"": ""https://www-api.aaa.com/api/EWFEWIFWEW=.json""

            }

        ]

    }

]

";

​

Console.WriteLine(JsonSerializer.Serialize<List<Root>>(JsonSerializer.Deserialize<List<Root>>(input)));

​

namespace Converter

{

    using System.Net.Http;

    using System.Text.Json.Serialization;

    public class UrlDownloaderConverter : JsonConverter<object>

    {

        public override bool CanConvert (Type t) => true;

        public override object Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

            => JsonSerializer.Deserialize(DownloadJson(reader.GetString()), typeToConvert, options);

​

        public override void Write(Utf8JsonWriter writer, object value, JsonSerializerOptions options)

            => JsonSerializer.Serialize(writer, value, value.GetType(), options);

​

        // You can mark as public to make DownloadJson globally accessible.

        private static string DownloadJson(string url)

        {

            using (HttpClient httpClient = new HttpClient())

            using (HttpResponseMessage msg = httpClient.GetAsync(url).Result)

            using (HttpContent content = msg.Content)

                return content.ReadAsStringAsync().Result;

        }

        public class FromURLAttribute : JsonConverterAttribute

        {

            public FromURLAttribute () : base (typeof(UrlDownloaderConverter)) {}

        }

    }

}

​

public class DateUrl

{

    public string aa { get; set; }

    public bool bb { get; set; }

    public bool? cc { get; set; }

}

​

public class Date

{

    // You will need a custom converter to convert the dates.

    public string a_date { get; set; }

    public bool push { get; set; }

    [FromURL]

    public List<DateUrl> date_url { get; set; }

}

​

public class Root

{

    public string title { get; set; }

    public List<Date> dates { get; set; }

}