Figure 5 The Compiler-generated Iterator
　

public class MyCollection : IEnumerable<string>
{
   public virtual IEnumerator<string> GetEnumerator()
   {
      GetEnumerator$0003__IEnumeratorImpl impl;
      impl = new GetEnumerator$0003__IEnumeratorImpl;
      impl.<this> = this;
      return impl; 
   }
   private class GetEnumerator$0003__IEnumeratorImpl : 
      IEnumerator<string>
   {
      public MyCollection <this>; // Back reference to the collection
      string $_current;
      // state machine members go here 
      string IEnumerator<string>.Current
      {
         get
         {
            return $_current;
         }
      }
      bool IEnumerator<string>.MoveNext()
      {
         //State machine management 
      }
      IDisposable.Dispose()
      {
         //State machine cleanup if required  
      }
   }
}