Can't figue out why the value didn't change : <p>I'm new to OOP and C#.</p>

<p>I've tried to use inheritance and encapsulation concepts and get stuck.</p>

<p>Can't figue out why a Deposit method din't work when i call it through Atm_1 class.</p>

<hr>

<p><strong><em>parent class</em></strong></p>

<pre><code>  class Atm
  {

    public int TotalBalance { get; private set; } = 1000;

    public Atm() { }

    public void DepoSit(int deposit)  { TotalBalance += deposit; }  

  }
</code></pre>

<p><strong><em>child class</em></strong></p>

<pre><code>  class Atm_1:Atm 
  {

  }
</code></pre>

<p><strong><em>main</em></strong></p>

<pre><code> class Program
 {

    static void Main()
    {


        var atm = new Atm();
        var atm_1 = new Atm_1();

       //Before Deposit 
        Console.WriteLine("Total Balance is "+atm.TotalBalance);     //1000

        //Deposit
        atm_1.DepoSit(20);

        //After Deposit
        Console.WriteLine("Total Balance is " + atm.TotalBalance);   //Still 1000 ??



        atm.DepoSit(500);
        Console.WriteLine("Total Balance is " + atm.TotalBalance);   //Now 1500
        //This Works -why the above didn't work?  

    }
}
</code></pre>
