Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Flurl;
using Flurl.Http;
using Newtonsoft.Json;
using SpotifyLibraryExporter.SpotifyAPI;

namespace SpotifyLibraryExporter
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var token = "<secret>";

            var lib = new List<SpotifyAPI.Track>();
            
            
            var spot = Library.FromJson(await "https://api.spotify.com/v1"
                .AppendPathSegments("me", "tracks")
                .SetQueryParam("offset", 0)
                .SetQueryParam("limit", 50)
                .WithOAuthBearerToken(token)
                .GetStringAsync());
            
            lib.AddRange(spot.Items.Select(x=>x.Track));
            Console.WriteLine($"Added offset {spot.Offset}...");

            while (spot.Next != null)
            {
                spot = Library.FromJson(await spot.Next.ToString()
                    .WithOAuthBearerToken(token)
                    .GetStringAsync());
                lib.AddRange(spot.Items.Select(x=>x.Track));
                Console.WriteLine($"Added offset {spot.Offset}...");
            }
            
            System.IO.File.WriteAllText(@"C:\Src\library.json", JsonConvert.SerializeObject(lib,Formatting.Indented));
            
            
        }
    }
}

SpotifyAPI.cs

// <auto-generated />
//
// To parse this JSON data, add NuGet 'Newtonsoft.Json' then do:
//
//    using SpotifyLibraryExporter.SpotifyAPI;
//
//    var library = Library.FromJson(jsonString);

using System.Net.Mime;

namespace SpotifyLibraryExporter.SpotifyAPI
{
    using System;
    using System.Collections.Generic;
    using System.Linq;

    using System.Globalization;
    using Newtonsoft.Json;
    using Newtonsoft.Json.Converters;

    public partial class Library
    {
        [JsonProperty("href")]
        public Uri Href { get; set; }

        [JsonProperty("items")]
        public Item[] Items { get; set; }

        [JsonProperty("limit")]
        public long Limit { get; set; }

        [JsonProperty("next")]
        public Uri Next { get; set; }

        [JsonProperty("offset")]
        public long Offset { get; set; }

        [JsonProperty("previous")]
        public Uri Previous { get; set; }

        [JsonProperty("total")]
        public long Total { get; set; }

        public override string ToString()
        {
            return $"Spotify Library response with {Total} items";
        }
    }

    public partial class Item
    {
        [JsonProperty("added_at")]
        public DateTimeOffset AddedAt { get; set; }

        [JsonProperty("track")]
        public Track Track { get; set; }

        public override string ToString()
        {
            return $"Track \"{Track}\" added on {AddedAt:g}";
        }
    }

    public partial class Track
    {
        [JsonProperty("album")]
        public Album Album { get; set; }

        [JsonProperty("artists")]
        public Artist[] Artists { get; set; }

        [JsonProperty("available_markets")]
        public string[] AvailableMarkets { get; set; }

        [JsonProperty("disc_number")]
        public long DiscNumber { get; set; }

        [JsonProperty("duration_ms")]
        public long DurationMs { get; set; }

        [JsonProperty("explicit")]
        public bool Explicit { get; set; }

        [JsonProperty("external_ids")]
        public ExternalIds ExternalIds { get; set; }

        [JsonProperty("external_urls")]
        public ExternalUrls ExternalUrls { get; set; }

        [JsonProperty("href")]
        public Uri Href { get; set; }

        [JsonProperty("id")]
        public string Id { get; set; }

        [JsonProperty("is_local")]
        public bool IsLocal { get; set; }

        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("popularity")]
        public long Popularity { get; set; }

        [JsonProperty("preview_url")]
        public Uri PreviewUrl { get; set; }

        [JsonProperty("track_number")]
        public long TrackNumber { get; set; }

        [JsonProperty("type")]
        public string Type { get; set; }

        [JsonProperty("uri")]
        public string Uri { get; set; }

        public override string ToString()
        {
            return $"{Name} by {String.Join(", ", Artists.Select(x => x.Name).ToArray())}";
        }
    }

    public partial class Album
    {
        [JsonProperty("album_type")]
        public string AlbumType { get; set; }

        [JsonProperty("artists")]
        public Artist[] Artists { get; set; }

        [JsonProperty("available_markets")]
        public string[] AvailableMarkets { get; set; }

        [JsonProperty("external_urls")]
        public ExternalUrls ExternalUrls { get; set; }

        [JsonProperty("href")]
        public Uri Href { get; set; }

        [JsonProperty("id")]
        public string Id { get; set; }

        [JsonProperty("images")]
        public Image[] Images { get; set; }

        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("release_date")]
        public string ReleaseDate { get; set; }

        [JsonProperty("release_date_precision")]
        public string ReleaseDatePrecision { get; set; }

        [JsonProperty("total_tracks")]
        public long TotalTracks { get; set; }

        [JsonProperty("type")]
        public string Type { get; set; }

        [JsonProperty("uri")]
        public string Uri { get; set; }
        
        public override string ToString()
        {
            return $"{Name} by {String.Join(", ", Artists.Select(x => x.Name).ToArray())}";
        }
    }

    public partial class Artist
    {
        [JsonProperty("external_urls")]
        public ExternalUrls ExternalUrls { get; set; }

        [JsonProperty("href")]
        public Uri Href { get; set; }

        [JsonProperty("id")]
        public string Id { get; set; }

        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("type")]
        public string Type { get; set; }

        [JsonProperty("uri")]
        public string Uri { get; set; }

        public override string ToString()
        {
            return Name;
        }
    }

    public partial class ExternalUrls
    {
        [JsonProperty("spotify")]
        public Uri Spotify { get; set; }

        public override string ToString()
        {
            return this.Spotify.ToString();
        }
    }

    public partial class Image
    {
        [JsonProperty("height")]
        public long Height { get; set; }

        [JsonProperty("url")]
        public Uri Url { get; set; }

        [JsonProperty("width")]
        public long Width { get; set; }

        public override string ToString()
        {
            return Url.ToString();
        }
    }

    public partial class ExternalIds
    {
        [JsonProperty("isrc")]
        public string Isrc { get; set; }
        
    }

    public partial class Library
    {
        public static Library FromJson(string json) => JsonConvert.DeserializeObject<Library>(json, SpotifyLibraryExporter.SpotifyAPI.Converter.Settings);
    }

    public static class Serialize
    {
        public static string ToJson(this Library self) => JsonConvert.SerializeObject(self, SpotifyLibraryExporter.SpotifyAPI.Converter.Settings);
    }

    internal static class Converter
    {
        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
        {
            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
            DateParseHandling = DateParseHandling.None,
            Converters =
            {
                new IsoDateTimeConverter { DateTimeStyles = DateTimeStyles.AssumeUniversal }
            },
        };
    }
}