using System;

public class Program

{

    public static void Main()

    {

        var ageProperty = new JsonIntProperty("age", 21);

        Console.WriteLine(ageProperty.StringRepresentation);

    }

}

​

public class JsonIntProperty

{

    private string characteristic;

    private int age;

    public JsonIntProperty(string chr, int agee)

    {

        characteristic = chr;

        age = agee ;

    }

    public string StringRepresentation

    {

        get { return $"{characteristic} : {age}"; }

    }

}