using System;

using System.Collections.Generic;

using Newtonsoft.Json;

​

public class Program

{

    public static void Main()

    {

        string input = @"{

    ""1"": 

    {

        ""CasaAutomobilistica"": ""Fiat"",

        ""Modello"": ""500"",

        ""AnnoImmatricolazione"": ""2017"",

        ""Targa"": ""AZ978AG"",

        ""KM"": 120000,

        ""Finanziamento"" : true,

        ""Porte"" : 5,

        ""Costo"" : 6000

    },

    ""2"":

    {

        ""CasaAutomobilistica"": ""BMW"",

        ""Modello"": ""Serie 1"",

        ""AnnoImmatricolazione"": ""2019"",

        ""Targa"": ""BC978AG"",

        ""KM"": 150000,

        ""Finanziamento"" : false,

        ""Porte"" : 3,

        ""Costo"" : 12000

    },

    ""3"":

    {

        ""CasaAutomobilistica"": ""Audi"",

        ""Modello"": ""A1"",

        ""AnnoImmatricolazione"": ""2016"",

        ""Targa"": ""BC978AG"",

        ""KM"": 200000,

        ""Finanziamento"" : true,

        ""Porte"" : 5,

        ""Costo"" : 15000

    }

}";

        var result = JsonConvert.DeserializeObject<Dictionary<string, Cars>>(input);

        result["3"].Dump(); // wont work outside of this web site

        result["3"].CustomDump(); // Work with the extention class at the bottom of this 

    }

​

    public partial class Cars

    {

        [JsonProperty("CasaAutomobilistica")]

        public string CasaAutomobilistica { get; set; }

​

        [JsonProperty("Modello")]

        public string Modello { get; set; }

​

        [JsonProperty("AnnoImmatricolazione")]

        [JsonConverter(typeof(ParseStringConverter))]

        public long AnnoImmatricolazione { get; set; }

​

        [JsonProperty("Targa")]

        public string Targa { get; set; }

​

        [JsonProperty("KM")]

        public long Km { get; set; }

​

        [JsonProperty("Finanziamento")]

        public bool Finanziamento { get; set; }

​

        [JsonProperty("Porte")]

        public long Porte { get; set; }

​

        [JsonProperty("Costo")]

        public long Costo { get; set; }

    }

    internal class ParseStringConverter : JsonConverter

    {

        public override bool CanConvert(Type t) => t == typeof(long) || t == typeof(long?);

​

        public override object ReadJson(JsonReader reader, Type t, object existingValue, JsonSerializer serializer)

        {

            if (reader.TokenType == JsonToken.Null) return null;

            var value = serializer.Deserialize<string>(reader);

            long l;

            if (Int64.TryParse(value, out l))

            {

                return l;

            }

            throw new Exception("Cannot unmarshal type long");

        }

​

        public override void WriteJson(JsonWriter writer, object untypedValue, JsonSerializer serializer)

        {

            if (untypedValue == null)

            {

                serializer.Serialize(writer, null);

                return;

            }

            var value = (long)untypedValue;

            serializer.Serialize(writer, value.ToString());

            return;

        }

​

        public static readonly ParseStringConverter Singleton = new ParseStringConverter();

    }

​

}

public static class ObjectExtention {

    public static void CustomDump<T>(this T data)

    {

        string json = JsonConvert.SerializeObject(data, Formatting.Indented);

        Console.WriteLine("Dumping object "+ typeof(T).Name+" :");

        Console.WriteLine(json);

    }

​

}