Simple C#,Multiple integer

[Abalfazl]

Hello!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace sepehr
{

    class zarb
    {
        public int i=10;
        int j=100;
        public void zarb1()
        {
             i = i *j;
        }

        public int zarb2
        {
            get { return i; }
        }

    }

    
    
    class test
    {
        static void Main(string[] args)
        {
           zarb k= new zarb();
            Console.WriteLine(k.zarb2);
            Console.ReadLine();

        
        }

    }
}

1-I expect it shows 1000,but it shows 10,

why?

2-I use this :

        public int zarb2
        {
            get { return i; }
        }

    }

Is it possible I don't use get{ return i;},instead of that I use

    class test
    {
        static void Main(string[] args)
        {
           zarb k= new zarb();
            Console.WriteLine(k.i);
            Console.ReadLine();

        
        }

another question:

using System;

class Unary
{
    public static void Main()
    {
        int unary = 0;
        int preIncrement;
        int preDecrement;
        int postIncrement;
        int postDecrement;
        int positive;
        int negative;
        sbyte bitNot;
        bool logNot;

        preIncrement = ++unary;
        Console.WriteLine("pre-Increment: {0}", preIncrement);

        preDecrement = --unary;
        Console.WriteLine("pre-Decrement: {0}", preDecrement);

        postdecrement = unary--;
        Console.WriteLine("Post-Decrement: {0}", postDecrement);

why does it use "{0}"?