How to use Observable.FromEvent with static events?

Question

I am trying to use Reactive Extensions to write code to handle an asynchronous call, where both the initiating method and the completed event are static. I can not use

var languageSetsLoaded = Observable .FromEvent<LoadLanguageSetsCompletedEventArgs>( LanguageManager, "LanguageSetsLoaded") 

since LanguageManager is a static class, not an instance, so I tried

 var languageSetsLoaded = Observable .FromEvent<LoadLanguageSetsCompletedEventArgs>( h => LanguageManager.LanguageSetsLoaded += h, h => LanguageManager.LanguageSetsLoaded -= h ) 

but it gives a syntax error "It is not possible to convert a lambda expression to an object type because it is not a delegate type." Event is declared in this way

 public delegate void LoadLanguageSetsCompletedHandler(LoadLanguageSetsCompletedEventArgs e); public static event LoadLanguageSetsCompletedHandler LanguageSetsLoaded = delegate { }; 

therefore, I believe that this is the type of delegate, and perhaps the fact that it is static creates an erroneous description of the error.

Is this their way of doing this, or will I just have to stick with non-reactive code like this?

 private void ChangeLanguage(string languageCode) { LanguageManager.LanguageSetsLoaded += OnLanguageSetsLoaded; LanguageManager.LoadLanguageSets(languageCode, BaseApp.InTranslationMode); } private void OnLanguageSetsLoaded(LoadLanguageSetsCompletedEventArgs e) { LanguageManager.LanguageSetsLoaded -= OnLanguageSetsLoaded; OnPropertyChanged("DummyLanguageResource"); } 

Answer 1

I think the problem is the type of delegate of your event. Try changing it to:

 public static event EventHandler<LoadLanguageSetsCompletedEventArgs> LanguageSetsLoaded = delegate { }; 

If you look at the Observable.FromEvent signature that you are trying to use, it looks like this:

 public static IObservable<IEvent<TEventArgs>> FromEvent<TEventArgs>( Action<EventHandler<TEventArgs>> addHandler, Action<EventHandler<TEventArgs>> removeHandler ) where TEventArgs : EventArgs 

Alternatively, you can use an overload with three arguments, the first of which is a conversion handler, but I think you would be better off just changing the event signature, if at all possible.