WhenAnyObservable is never having any effect on the command

[fahadash]

Alright this is crazy, tell me what I am doing wrong here, I have the following code (it is supposed to toggle enable/disable a command every two seconds)

           ISubject<bool> fileSystemOperationRunning = new Subject<bool>();

            var xxx =

                Observable.Interval(TimeSpan.FromSeconds(2.0)).Select(_ => true)

                    .Scan( (p, n) => !p)

                    ..CombineLatest(fileSystemOperationRunning, (a, b) => a && !b)

                .ObserveOn(RxApp.MainThreadScheduler);

            xxx.Trace("TEST1");

            var startTextAnalysis = ReactiveCommand.CreateAsyncTask(

                    xxx,

                _ => RunTextAnalysis());

            StartTextAnalysis = startTextAnalysis;

            startTextAnalysis.IsExecuting.Subscribe(fileSystemOperationRunning);

       fileSystemOperationRunning.OnNext(false);

Here is the trace output

TEST1 : True

TEST1 : False

TEST1 : True

TEST1 : False

TEST1 : True

But my Button stays disabled.

If I remove the following part, it works

                    ..CombineLatest(fileSystemOperationRunning, (a, b) => a && !b)

Why ?