Remove an IObservable from merged sequence - wpf

Question

I am using Observable.Merge to combine multiple sequences and display in a single view in UI. Users can choose to add or remove sequences(feeds) in the UI. While I have used Merge to combine feeds. I am not sure how I can detach an IObservable from a Merged sequence. Currently I am creating a brand new IObservable omitting the feeds I want to. Is it possible to dynamically add and remove to an IObsevable that the ViewModel has already subscribed to?

Answer 1

Take a look at using IObservable<IObservable<T>> and then use Merge. This automatically allows you to remove a sequence by ending the inner IObservable<T>. Simple.

Answer 2

Something like this would also work, but I suspect there are neater ways.
class Merger<T>
{
Subject<T> _merged = new Subject<T>();
public IObservable<T> Merged { get { return _merged; } }
public IDisposable Add(IObservable<T> newStream)
{
return newStream.Subscribe(_merged);
}
}
To remove something from the merged stream, dispose of the IDisposable.

Answer 3

This might help get you started, but on reconnection, because b is cold, b will restart from the beginning:
var a = Observable.Generate('A', x => x <= Char.MaxValue, x => ++x, x => x, x => TimeSpan.FromMilliseconds(200)).Select(x => "a: " + x).Publish();
var b = Observable.Generate('a', x => x <= Char.MaxValue, x => ++x, x => x, x => TimeSpan.FromMilliseconds(500)).Select(x => "b: " + x).Publish();
var merged = a.Merge(b).Publish();
var submerged = merged.Subscribe(x => x.Dump());
var subA = a.Connect();
var subB = b.Connect();
merged.Connect();
Task.Delay(2000).ContinueWith(t => subB.Dump("Disposing b.").Dispose());
Task.Delay(4000).ContinueWith(t => b.Connect()).ContinueWith(_ => "Reconnected to b");
EDIT:
To add another 'c' to the merged IO:
var a = Observable.Generate('A', x => x <= Char.MaxValue, x => ++x, x => x, x => TimeSpan.FromMilliseconds(200)).Select(x => "a: " + x).Publish();
var b = Observable.Generate('a', x => x <= Char.MaxValue, x => ++x, x => x, x => TimeSpan.FromMilliseconds(500)).Select(x => "b: " + x).Publish();
var c = Observable.Generate('1', x => x <= Char.MaxValue, x => ++x, x => x, x => TimeSpan.FromMilliseconds(100)).Select(x => "c: " + x).Publish();
var merged = a.Merge(b).Merge(c).Publish();
var submerged = merged.Subscribe(x => x.Dump());
var subA = a.Connect();
var subB = b.Connect();
merged.Connect();
Task.Delay(2000).ContinueWith(t => subB.Dump("Disposing b.").Dispose());
Task.Delay(4000).ContinueWith(t => b.Connect()).ContinueWith(_ => "Reconnected to b".Dump());
Task.Delay(6000).ContinueWith(t => c.Connect()).ContinueWith(_ => "Connecting to c".Dump());