using System;

using System.Collections;

using System.Collections.Generic;

​

var coll = new MyCollection<string>(new []{

   "I", "love", "my", "instructor"

});

foreach(string s in coll)

   Console.Write($"{s} ");

​

class MyCollection<T> : IEnumerable<T>

{

   T[] elems;

   public MyCollection(T [] src)

   {

      // let's hope T is immutable... I love C++

      elems = new T[src.Length];

      for(int i = 0; i != src.Length; ++i)

         elems[i] = src[i];

   }

   class En : IEnumerator<T>

   {

      T [] elems;

      int cur = -1;

      public void Reset() {}

      public void Dispose() {}

      public En(T [] src)

      {

         elems =src;

      }

      public T Current => elems[cur];

      object IEnumerator.Current => elems[cur];

      public bool MoveNext()

      {

         if(cur == elems.Length - 1) return false;

         ++cur;

         return true;

      }

   }

   public IEnumerator<T> GetEnumerator() => new En(elems);

   IEnumerator IEnumerable.GetEnumerator() => new En(elems);

}

​