using System;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        var json = @"

        {

            ""item"": {

                ""foo"": ""4"",

                ""bar"": ""42""

            }

        }

        ";

        var jO = JObject.Parse(json);

        var jToken = jO["item"]["foo"];

        jToken.GetType().Name.Dump("jToken type");

        //jToken = "5";

        ((JValue)jToken).Value = "5";

        jO.ToString().Dump("jO");

        jToken.Dump("jToken");

    }

}

​

public static class Shim

{

    public static void Dump(this object obj, string heading)

    {

        Console.WriteLine(heading);

        Console.WriteLine(obj.ToString());

        Console.WriteLine();

    }

}