TaskObservableExtensions
public static IObservable<TResult> ToObservable<TResult>(this Task<TResult> task, IScheduler scheduler)
public static Task<TResult> ToTask<TResult>(this IObservable<TResult> observable, CancellationToken cancellationToken)
public static Task<TResult> ToTask<TResult>(this IObservable<TResult> observable, CancellationToken cancellationToken, object state)