RX Observable.TakeWhile checks condition BEFORE each element but I need to perform the check after

Question

Observable.TakeWhile allows you to run a sequence as long as a condition is true (using a delegate so we can perform computations on the actual sequence objects), but it\'s

Answer 1

There's no built in operators to do what you're asking, but here's one that uses Publish to run two queries while only subscribing to the underlying observable once:

// Emits matching values, but includes the value that failed the filter
public static IObservable TakeWhileInclusive(
    this IObservable source, Func predicate)
{
    return source.Publish(co => co.TakeWhile(predicate)
        .Merge(co.SkipWhile(predicate).Take(1)));
}

And then:

var obs = listOfCommands.ToObservable()
    .TakeWhileInclusive(c.CurrentIndex != c.TotalCount);