public static IAsyncObservable <TSource> ElementAt <TSource>(this IAsyncObservable <TSource> source, int index)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (index < 0)
{
throw new ArgumentOutOfRangeException(nameof(index));
}
return(Create <TSource>(observer => source.SubscribeSafeAsync(AsyncObserver.ElementAt(observer, index))));
}