protected override IDisposable SubscribeCore(IObserver <T> observer)
{
if (_subject.Value != null)
{
observer.OnNext(_subject.Value !);
return(Disposable.Empty);
}
// Keep taking values until a non-null value is received and only emit that one.
return(_subject.TakeUntil(value => value != null).LastAsync().Subscribe(value => {
Debug.Assert(value != null, "value != null");
observer.OnNext(value !);
}, observer.OnError, observer.OnCompleted));
}
