namespace System.Reactive.Linq.ObservableImpl { internal sealed class If<TResult> : Producer<TResult, If<TResult>._>, IEvaluatableObservable<TResult> { internal sealed class _ : IdentitySink<TResult> { private readonly If<TResult> _parent; public _(If<TResult> parent, IObserver<TResult> observer) : base(observer) { _parent = parent; } public void Run() { IObservable<TResult> source; try { source = _parent.Eval(); } catch (Exception error) { ForwardOnError(error); return; } SetUpstream(ObservableExtensions.SubscribeSafe<TResult>(source, (IObserver<TResult>)this)); } } private readonly Func<bool> _condition; private readonly IObservable<TResult> _thenSource; private readonly IObservable<TResult> _elseSource; public If(Func<bool> condition, IObservable<TResult> thenSource, IObservable<TResult> elseSource) { _condition = condition; _thenSource = thenSource; _elseSource = elseSource; } public IObservable<TResult> Eval() { if (!_condition()) return _elseSource; return _thenSource; } protected override _ CreateSink(IObserver<TResult> observer) { return new _(this, observer); } protected override void Run(_ sink) { sink.Run(); } } }