Clase que implementa la interfaz IEnumerator.

GenteEnumerator.cs

using System.Collections;
using System;

namespace cap07.usoienumerator
{
    public class GenteEnumerator : IEnumerator
    {
        public Persona[] personas;

        int position = -1;

        public GenteEnumerator(Persona[] personas)
        {
            this.personas = personas;
        }

        public bool MoveNext()
        {
            ++position;
            return (position < personas.Length);
        }

        public void Reset()
        {
            position = -1;
        }

        object IEnumerator.Current
        {
            get
            {
                return Current;
            }
        }

        public Persona Current
        {
            get
            {
                try
                {
                    return personas[position];
                }
                catch (IndexOutOfRangeException)
                {
                    throw new InvalidOperationException();
                }
            }
        }
    }
}