C#•2y ago

Events and Delegates [Answered]

I'm encountering a very strange error. I have a delegate and an event inside my IAuthService. Now when other class are trying to inherit from the interface. For some reason I have to implement the event explicitly? The first one is working fine! But the second one is complaining for some reason.

16 Replies

Monsieur Wholesome•2y ago

Btw, put that delegate definition out of there It's not a class member, but kind of a type definition on its own

333fred•2y ago

I mean, it can be Can you show the definition of IAuthService?

Monsieur Wholesome•2y ago

It's not bound to an interface contract + every single implementing type would theoretically define the same delegate

SwaggerLife•2y ago

looks like this

    internal interface IAuthService
    {
        delegate void AccountCreatedEventHandler(object source, AccountCreatedEventArgs args);
        
        event AccountCreatedEventHandler? AccountCreated;
    }

    internal interface IAuthService
    {
        delegate void AccountCreatedEventHandler(object source, AccountCreatedEventArgs args);
        
        event AccountCreatedEventHandler? AccountCreated;
    }

333fred•2y ago

Yep, ok So, here's what's happening Your AccountCreated in AuthService has a return type of AuthService.AccountCreatedEventHandler What it actually needs to be is IAuthService.AccountCreatedEventHandler

SwaggerLife•2y ago

Yes But I don't get it

333fred•2y ago

Just straight up remove the AccountCreatedEventHandler delegate in AuthService AuthService.AccountCreatedEventHandler != IAuthService.AccountCreatedEventHandler Those are completely separate types

Monsieur Wholesome•2y ago

When declaring a delegate, youre declaring it as if it was a class You declare it once, and now you can use that delegate It's not a per-class member

SwaggerLife•2y ago

Yes it seems like I don't need to even have the delegate inside the AuthService. But I would be lying if I said I understood the event thing. AuthService.AccountCreatedEventHandler != IAuthService.AccountCreatedEventHandler I get that they don't have the same types. But for the other part it's still a bit confusing.

333fred•2y ago

The other part?

SwaggerLife•2y ago

I mean normally when I implement a method from an Interface. It doesn't force me to Implement it explicitly? This is the part which is confusing to me. Maybe I have misunderstood the entire concept.

333fred•2y ago

You're not implementing explicitly You're saying "The return type is the AccountCreatedEventHandler defined in IAuthService"

Monsieur Wholesome•2y ago

You defined the same delegate twice, now in the ~~deriving~~ implementing class you mentioned the delegate name And thus it prioritized the one from right below it, though the interface means the one from the interface That's why you had to explicitly mention "the one from the interface"

333fred•2y ago

For explicit implementation, the Interface. goes on the method/property name, not on a type Explicit implementation would have looked like this:

event IAuthService.AccountCreatedEventHandler IAuthService.AccountCreated;

event IAuthService.AccountCreatedEventHandler IAuthService.AccountCreated;

SwaggerLife•2y ago

Oh shit I get it know. Stupid me. Thank you very much guys.

Accord•2y ago

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Events and Delegates [Answered]