using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Serialization;

public class Program

{

    public static void Main()

    {

        var dict = new Dictionary<string, object>();

        dict.Add("شماره قرائت قبلی", 4123);

        dict.Add("قطر انشعاب آب", "1/2اینچ");

        var json = JsonConvert.SerializeObject(dict);

        Console.WriteLine(json);

        var m = JsonConvert.DeserializeObject<AdditionalModel>(json);

        Console.WriteLine(m.NoRead);

        Console.WriteLine(m.Diameter);

    }

}

​

public class AdditionalModel

{

    [JsonProperty("شماره قرائت قبلی")]

    public string NoRead { get; set; }

    [JsonProperty("قطر انشعاب آب")]

    public string Diameter { get; set; }

}