How to call async methods from within a Prism event aggregator subscriber?

Question

Quick question - how do I call async methods from within a Prism event aggregator subscriber action? E.g.

_eventAggregator.GetEvent<PubSubEvent<SomeMessage>>()
   .Subscribe((msg) => {
                       DoSomething();
                       await DoSomethingAsync();
                       DoSomethingElse();
                    });

You can stick async in front of your lambda e.g. async (msg) => { ... }, but Subscribe won't wait for it to complete. — Charles Mager
– Charles Mager, Commented Jun 9, 2016 at 12:13
@CharlesMager this will create async void which is not recommended solution. — Karel Kral
– Karel Kral, Commented Dec 3, 2018 at 14:46

Karel Kral · Accepted Answer · 2018-12-03 14:58:15Z

3

With current Prism implementation, it is not possible see here.

But I have found an alternate implementation of Prism's EventAggregator, which allows async subscriptions. See here.

This new event async aggregator overloads can be used in the same way as the original one:

Subscription to event is exactly the same with another overload:


    _eventAggregator.GetEvent<<TfsHookEvent<WorkItemUpdatedPayload>>().Subscribe(WorkItem_Updated);

Event handler:


    private async Task WorkItem_Updated(WorkItemUpdatedPayload obj)
    {
        await CheckAsync();
    }

edited Dec 3, 2018 at 14:58

answered Dec 3, 2018 at 14:53

Karel Kral

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2 Comments

DirtyNative Over a year ago

How do we include those classes? There does not seem to be a Nuget package, and simply pasting the necessary files into my own solution results in conflicting classes

Karel Kral Over a year ago

I downloaded Prism sources and replaced files from the source above. Not an ideal solution. There is no NuGet package.

LeRoy · Accepted Answer · 2017-12-01 12:47:40Z

2

Just making @Charles Mager a answer

_eventAggregator.GetEvent<PubSubEvent<SomeMessage>>()
   .Subscribe(async(msg) => {
                       DoSomething();
                       await DoSomethingAsync();
                       DoSomethingElse();
                    });

answered Dec 1, 2017 at 12:47

LeRoy

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2 Comments

Emy Ferreira Over a year ago

Will it create async void method from this lambda method ? Isn't it not recommended ?

Karel Kral Over a year ago

No, this is no good solution. It works but it is a "fire and forget" style. No exceptions are caught.

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