CollectionBase

namespace MyCollectionBase
{
    using System.Collections;

    class Program
    {
        static void Main(string[] args)
        {
            myCollection c = new myCollection();
            c.Add("DSC");
            c.Add("CSC");
            c.Add("BSC");
            c.Add("ASC");
            foreach (string item in c)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine(c.Length());
            Console.ReadKey();
        }
    }
    class myCollection : CollectionBase
    {

        public void Add(object item)
        {
            InnerList.Add(item);
        }
        public int Length()
        {
            return InnerList.Count;
        }
        public void Delete(object item)
        {
            InnerList.Remove(item);
        }
        public void Clear()
        {
            InnerList.Clear();
        }
    }
}