using System;

​

public class Foo

{

    public int X { get; } = 0;

​

    public Foo() { }

    public Foo(int x) {

        this.X = x;

    }

}

public class Program

{

    public static void Main()

    {

        var foo0 = new Foo();

        Console.WriteLine(foo0.X);

        var foo7 = new Foo(7);

        Console.WriteLine(foo7.X);

    }

}