Boxing / Cast, Interfact, Abstract, Concrete

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

namespace ConsoleApplication1
{
    class Program
    {
        interface IText
        {
            string ToText();
        }
        class Subtip : SubtitleFormat, IText
        {
            public int Error { get; set; }

            public Subtip(int error)
            {
                Error = error;
            }
            public string ToText()
            {
                return $"{Error}, Hello!";
            }
        }
        abstract class SubtitleFormat
        {
            protected int _errorCount = 1;

            public int ErrorCount
            {
                get
                {
                    return _errorCount;
                }
            }
        }
        static void Main(string[] args)
        {
            SubtitleFormat sb = new Subtip(10);
            IText sb2 = sb as IText;

            Console.WriteLine(sb.ErrorCount);
            Console.WriteLine((sb as Subtip).Error);
            Console.WriteLine(sb2.ToText());
            Console.ReadLine();
        }
    }
}