namespace System.Reactive.Linq.ObservableImpl { internal sealed class SumDoubleNullable : Producer<double?, SumDoubleNullable._> { internal sealed class _ : Sink<double?>, IObserver<double?> { private double _sum; public _(IObserver<double?> observer, IDisposable cancel) : base(observer, cancel) { _sum = 0; } public void OnNext(double? value) { if (value.HasValue) _sum += value.Value; } public void OnError(Exception error) { _observer.OnError(error); base.Dispose(); } public void OnCompleted() { _observer.OnNext(_sum); _observer.OnCompleted(); base.Dispose(); } } private readonly IObservable<double?> _source; public SumDoubleNullable(IObservable<double?> source) { _source = source; } protected override _ CreateSink(IObserver<double?> observer, IDisposable cancel) { return new _(observer, cancel); } protected override IDisposable Run(_ sink) { return _source.SubscribeSafe(sink); } } }