How Can I Unfold This Event to an Observable Sequence?

Question

I'm trying to write an Add-In for Outlook, and one of the events I'm using is ItemsEvents_Event.ItemChange - and its handler's signature takes an Object as a parameter (the item that changed):

items.ItemChange += CalendarItems_ItemChange;

private void CalendarItems_ItemChange(object anItem) {...}

How would I use Observable.FromEvent or Observable.FromEventPattern to create an observable sequence from this event "stream" instead of attaching/detaching the event as usual?

score 2 · Accepted Answer · edited May 23 '17 at 12:29

You need to use the FromEvent conversion overload to tell Rx how it should interpret your event:

IObservable<TEventArgs> FromEvent<TDelegate, TEventArgs>(Func<Action<TEventArgs>, TDelegate> conversion, 
                                                         Action<TDelegate> addHandler, 
                                                         Action<TDelegate> removeHandler);

In your case it would look like:

var source = Observable.FromEvent<ItemsEvents_ItemEventChangeHandler, object>(
  emit => new ItemsEvents_ItemEventChangeHandler((obj) => emit(obj)),
  h => items.ItemChange += h,
  h => items.ItemChange -= h);

How Can I Unfold This Event to an Observable Sequence?

1 Answers1