using System;

using Newtonsoft.Json;

public class Program

{

    public record Asset(string browser_download_url);

    public record Release(Asset[] assets);

    public static void Main()

    {

        var input = @"

[

  {

    ""assets"": [

      {

        ""browser_download_url"": ""foo""

      }

    ]

  }

]";

        var body = JsonConvert.DeserializeObject<Release[]>(input);

        var test = body[0].assets[0].browser_download_url;

        Console.WriteLine(test.ToString());

    }

}