Some C# funny read only properties testing

using System;
using System.Globalization;

namespace CSharpTest
{
    class PropertiesTesting
    {
        private int somePrivateVar;

        public string SomePrivateThing { get; } // read only property
        public int SomePrivateVar { get; } //


        public PropertiesTesting(string var) => SomePrivateThing = var; // ctor can change it
        public PropertiesTesting(int var) => SomePrivateVar = var; // ctor can change this one too

        //public void ChangeSomEPrivateThing() => SomePrivateThing = "gg"; // but method can't
        //public void ChangeSomePrivateVar() => SomePrivateVar = 1; // also can't

        public void ChangeSomePrivateVar() => somePrivateVar = 1; // but we can do this!
        /*
         but there is the problem: in this case we should manually specify that value will be linked with property
         or there will be two different entities, so in this case
         "somePrivateVar"(field) and "SomePrivateVar"(property) aren't same object

         we will show how it should be done for var value and Var property in Entity class
             */

        public void showData()
        {
            Console.WriteLine($"SomePrivateThing = {SomePrivateThing}");
            Console.WriteLine($"SomePrivateVar = {SomePrivateVar}");
            Console.WriteLine($"somePrivateVar = {somePrivateVar}");
        }
    }

    class Entity
    {
        private int var; // field
        public int Var => var; // read only property

        //public Entity(int value) => Var = value; here ctor already can't initialize read only property
        public Entity(int value) => var = value; // but it can initialize field

        // same to methods
        //public void Method() => Var = 100; there is no way!
        public void Method() => var = 100; // here it is!

        public void showData() => Console.WriteLine($"var = {var}\nVar = {Var}");
    }

    class Program
    {
        static void Main(string[] args)
        {
            CultureInfo.CurrentCulture = new CultureInfo("en-US", false);

            PropertiesTesting pt = new PropertiesTesting("auf");
            // pt.SomePrivateThing = "awooooo!"; can't do such stuff - compile error

            PropertiesTesting pt2 = new PropertiesTesting(100);
            pt2.ChangeSomePrivateVar();
            pt2.showData(); // "", 100 and 1

            Entity e = new Entity(5);
            e.showData(); // 5 and 5
            e.Method();
            e.showData(); // 100 and 100 as it should be

            Console.ReadKey();
        }
    }
}