System.Reactive.Subjects.ISubject<TSource, TResult>

public interface ISubject<TSource, TResult> : IObserver<TSource>, IObservable<TResult>

Represents an object that is both an observable sequence as well as an observer.

namespace System.Reactive.Subjects { public interface ISubject<in TSource, out TResult> : IObserver<TSource>, IObservable<TResult> { } }