C# Language
Usando json.net

Introducción

Usando JsonConverter en valores simples

Ejemplo de uso de JsonCoverter para deserializar la propiedad de tiempo de ejecución de la respuesta de la API en un objeto de intervalo de tiempo en el modelo de películas

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"
}

Modelo de película

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);
        }
    }
}

Llamándolo

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

Recoge todos los campos del objeto JSON

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;
}

Uso:

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}'");

Manifestación
Para este objeto JSON

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

La salida esperada será:

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