Notification when ReactiveCommand completes - system.reactive

Question

I'm trying to use ReactiveUI ReactiveCommands to switch on and off a gRPC stream that I've converted into an observable.
The code shown below works to some extent - the connect button will cause the stream to connect, and I start receiving data in the onNext handler of the subscribe. The disconnect button does also disconnect the stream via the cancellation token.
However, once the disconnect command is executed, I would also like to be notified so I can clear up some other state in the application. I understand that the onCompleted of the ReactiveCommand never gets called, because at any point it could be executed again, so my question is - how can I know when the stream has been switched off?
View
this.WhenActivated(d =>
{
d(this.BindCommand(ViewModel, x => x.ConnectCommand, x => x.Connect));
d(this.BindCommand(ViewModel, x => x.DisconnectCommand, x => x.Disconnect));
});
ViewModel
ConnectCommand = ReactiveCommand.CreateFromObservable(
() => appService.ApplicationStream(request)
.TakeUntil(DisconnectCommand));
ConnectCommand.Subscribe(
resp =>
{
_logger.Debug(resp);
},
() =>
{
// Ideally I could do something useful here, but https://stackoverflow.com/a/26599880/57215
_logger.Debug("Never called, ReactiveCommands never OnComplete");
});
ConnectCommand.IsExecuting.Subscribe(x => _logger.Debug($"is executing: {x}"));
ConnectCommand.CanExecute.Subscribe(x => _logger.Debug($"can execute: {x}"));
ConnectCommand.ThrownExceptions.Subscribe(ex =>
throw new Exception($"Could not get data from server: {ex}"));
DisconnectCommand = ReactiveCommand.Create(
() => { },
ConnectCommand.IsExecuting);
Service
public IObservable<ApplicationStreamResponse> ApplicationStream(ApplicationStreamRequest request)
{
return Observable.Create<ApplicationStreamResponse>(async (observer, token) =>
{
try
{
using (var call = _client.ApplicationStream(request, cancellationToken: token))
{
while (await call.ResponseStream.MoveNext())
{
if (token.IsCancellationRequested) return;
observer.OnNext(call.ResponseStream.Current);
}
observer.OnCompleted();
}
}
catch (RpcException e)
{
if (e.Status.StatusCode == StatusCode.Cancelled)
{
_logger.Debug($"Application stream was disconnected: {e.Status.Detail}");
observer.OnCompleted();
}
observer.OnError(e);
}
});
}

Answer 1

Subscribe to the command:
d(this.BindCommand(ViewModel, x => x.DisconnectCommand, x => x.Disconnect));
this.ViewModel.DisconnectCommand
.Subscribe(_ => { /* command finished */});
Or create a bool reative property, set it to true at the end of the DisconnectCommand code, and check the value in the view.