gistfile1.cs

namespace ForEachWithOnlyGetEnumerator
{
    using System;
    using System.Collections;

    class Foo
    {
        public IEnumerator GetEnumerator()
        {
            yield return "foo";
            yield return "bar";
            yield return "baz";
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            foreach(var item in new Foo())
            {
                Console.WriteLine(item);
            }
        }
    }
}