using System;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        var a = "{ \"Name\": \"DHWTemp\", \"Value\": 2.4}";

        var datapoint = JsonConvert.DeserializeObject<Datapoint>(a);

        var casted = (double)datapoint.Value;

        Console.WriteLine(datapoint.Value.ToString());

        Console.WriteLine(casted);

    }

}

​

public class Datapoint

{

    public string Name {get; set;}

    public object Value {get; set;}

}