C# | Using json.net

Using JSON.net JsonConverter class.

Using JsonConverter on simple values

Example using JsonCoverter to deserialize the runtime property from the api response into a Timespan Object in the Movies model

JSON (http://www.omdbapi.com/?i=tt1663662))

{
    Title: "Pacific Rim",
    Year: "2013",
    Rated: "PG-13",
    Released: "12 Jul 2013",
    Runtime: "131 min",
    Genre: "Action, Adventure, Sci-Fi",
    Director: "Guillermo del Toro",
    Writer: "Travis Beacham (screenplay), Guillermo del Toro (screenplay), Travis Beacham (story)",
    Actors: "Charlie Hunnam, Diego Klattenhoff, Idris Elba, Rinko Kikuchi",
    Plot: "As a war between humankind and monstrous sea creatures wages on, a former pilot and a trainee are paired up to drive a seemingly obsolete special weapon in a desperate effort to save the world from the apocalypse.",
    Language: "English, Japanese, Cantonese, Mandarin",
    Country: "USA",
    Awards: "Nominated for 1 BAFTA Film Award. Another 6 wins & 46 nominations.",
    Poster: "https://images-na.ssl-images-amazon.com/images/M/MV5BMTY3MTI5NjQ4Nl5BMl5BanBnXkFtZTcwOTU1OTU0OQ@@._V1_SX300.jpg",
    Ratings: [{
            Source: "Internet Movie Database",
            Value: "7.0/10"
        },
        {
            Source: "Rotten Tomatoes",
            Value: "71%"
        },
        {
            Source: "Metacritic",
            Value: "64/100"
        }
    ],
    Metascore: "64",
    imdbRating: "7.0",
    imdbVotes: "398,198",
    imdbID: "tt1663662",
    Type: "movie",
    DVD: "15 Oct 2013",
    BoxOffice: "$101,785,482.00",
    Production: "Warner Bros. Pictures",
    Website: "http://pacificrimmovie.com",
    Response: "True"
}

Movie Model

using Project.Serializers;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.Threading.Tasks;

namespace Project.Models
{
    [DataContract]
    public class Movie
    {
        public Movie() { }

        [DataMember]
        public int Id { get; set; }

        [DataMember]
        public string ImdbId { get; set; }

        [DataMember]
        public string Title { get; set; }

        [DataMember]
        public DateTime Released { get; set; }

        [DataMember]
        [JsonConverter(typeof(RuntimeSerializer))]
        public TimeSpan Runtime { get; set; }

    }
}

RuntimeSerializer

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace Project.Serializers
{
    public class RuntimeSerializer : JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return objectType == typeof(TimeSpan);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            if (reader.TokenType == JsonToken.Null)
                return null;

            JToken jt = JToken.Load(reader);
            String value = jt.Value<String>();

            Regex rx = new Regex("(\\s*)min$");
            value = rx.Replace(value, (m) => "");

            int timespanMin;
            if(!Int32.TryParse(value, out timespanMin))
            {
                throw new NotSupportedException();
            }

            return new TimeSpan(0, timespanMin, 0);
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            serializer.Serialize(writer, value);
        }
    }
}

Calling It

Movie m = JsonConvert.DeserializeObject<Movie>(apiResponse));

Collect all fields of JSON object

using Newtonsoft.Json.Linq;
using System.Collections.Generic;

public class JsonFieldsCollector
{
    private readonly Dictionary<string, JValue> fields;

    public JsonFieldsCollector(JToken token)
    {
        fields = new Dictionary<string, JValue>();
        CollectFields(token);
    }

    private void CollectFields(JToken jToken)
    {
        switch (jToken.Type)
        {
            case JTokenType.Object:
                foreach (var child in jToken.Children<JProperty>())
                    CollectFields(child);
                break;
            case JTokenType.Array:
                foreach (var child in jToken.Children())
                    CollectFields(child);
                break;
            case JTokenType.Property:
                CollectFields(((JProperty) jToken).Value);
                break;
            default:
                fields.Add(jToken.Path, (JValue)jToken);
                break;
        }
    }

    public IEnumerable<KeyValuePair<string, JValue>> GetAllFields() => fields;
}

Usage:

var json = JToken.Parse(/* JSON string */);
var fieldsCollector = new JsonFieldsCollector(json);
var fields = fieldsCollector.GetAllFields();

foreach (var field in fields)
    Console.WriteLine($"{field.Key}: '{field.Value}'");

Demo
For this JSON object

{
  "User": "John",
  "Workdays": {
    "Monday": true,
    "Tuesday": true,
    "Friday": false
  },
  "Age": 42
}

expected output will be:

User: 'John'
Workdays.Monday: 'True'
Workdays.Tuesday: 'True'
Workdays.Friday: 'False'
Age: '42'