private static IAsyncQueryable <NuGetPackage> Synchronized(IAsyncQueryable <NuGetPackage> async, Func <IQueryable <NuGetPackage>, IQueryable <NuGetPackage> > getNotEvaluated) { var syncTask = AsyncEnumerableExtensions.ToList(async); syncTask.Wait(); var completedList = syncTask.Result; var withFilter = getNotEvaluated(completedList.AsQueryable()); var completedEnumer = new CompletedAsyncEnumerator <NuGetPackage>(withFilter); return(AsyncEnumerable.FromResult(completedEnumer)); }