public readonly Func<T, IEnumerator> Func;
       public readonly T Context;

       public IEnumerator YieldInvoke()
        {
            var awaitable = Context as IAwaitable;
            if (awaitable != null)
            {
                awaitable.Completed = false;
            }
            yield return Func(Context);
            if (awaitable != null)
            {
                awaitable.Completed = true;
            }
        }

       public readonly Func<T, IEnumerator> Func;
       public readonly T Context;

       public IEnumerator YieldInvoke()
        {
            var awaitable = Context as IAwaitable;
            if (awaitable != null)
            {
                awaitable.Completed = false;
            }
            yield return Func(Context);
            if (awaitable != null)
            {
                awaitable.Completed = true;
            }
        }

                            try
                            {
                                next = enumerator.MoveNext();
                            }
                            catch (Exception e)
                            {
                                exception = e;
                                goto onError;
                            }
                             if (next)
                            {
                                yield return enumerator.Current;
                            }

                            try
                            {
                                next = enumerator.MoveNext();
                            }
                            catch (Exception e)
                            {
                                exception = e;
                                goto onError;
                            }
                             if (next)
                            {
                                yield return enumerator.Current;
                            }