using System;

namespace ConsoleApp1
{
    struct Mutable
    {
        public Mutable(int x, int y)
            : this()
        {
            X = x;
            Y = y;
        }
        public void IncrementX() { X++; }
        public int X { get; private set; }
        public int Y { get; set; }
    }
    class A
    {
        public A() { Mutable = new Mutable(x: 5, y: 5); }
        public Mutable Mutable { get; private set; }
    }


    internal class Program
    {
        private static void Main(string[] args)
        {
            A a = new A();

            Console.WriteLine(a.Mutable.X);

            a.Mutable.IncrementX();

            Console.WriteLine(a.Mutable.X);

            Console.ReadKey();
        }
    }
}