C#•16mo ago

❔ Getting all instances from a IServiceScope

I have a callback system that I want to ensure all subscribers are removed from when a dependency scope is destroyed. To achive this I want to itterate over all instanciated class and unregister them. But I am struggeling with getting all created instances from the IServiceScope. I cant cast to ServiceProviderEngineScope, as that is a sealed internal class. How does one normally access this information?

12 Replies

Sossenbinder•16mo ago

You could have the affected classes inherit from IDisposable If a scope is disposed, it will dispose all the disposables inside as well

Ole (ping please)OP•16mo ago

That was my frist thought, but then I need to store the event subscriber class so I can call it from dispose. I never need it outside of dispose and the construtor so it would be kind of neat to have a void Unregister(EventHub hub) function in a interface

Sossenbinder•16mo ago

Ah What could also work: Register your services towards an interface containing your method And then you can resolve IEnumerable<IInterface> That will resolve all instances registered for that interface

Ole (ping please)OP•16mo ago

But that has the potential to be very inefficient? For a given scope there might be 500 potential classes, but depending on the incomming request, the path taken might only instanciate 5. Doing it that way will force the instanciation of all.

Sossenbinder•16mo ago

Oh, I see now, so you want to get the "alive" objects. I'm not sure if there's a way to do this with MS DI, I know Autofac etc. have interceptor features. I guess with MS DI you would have to have some kind of tracker service injected into all others Not sure if there's a way to write an interceptor around ServiceProvider

Ole (ping please)OP•16mo ago

I cant find a way of doing it, which is a bit strange. I agree its a bit of a corner case but it cant be that unusual. Would be good for some logging cases as well I would assume

Unknown User•16mo ago

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Mayor McCheese•16mo ago

https://learn.microsoft.com/en-us/dotnet/api/system.iobservable-1?view=net-7.0

Ole (ping please)OP•16mo ago

Because it requires me to store the variable. It means I would have to write something like this:

class MyClass : IDisposable
{
    EventHub _hub;

    public MyClass(EventHub hub)
    {
        _hub = hub;
        _hub.Subscribe<ItemSaved>(this, OnSaved);
    }
    
    public void Dispose() => _hub.Remove(this);
}

class MyClass : IDisposable
{
    EventHub _hub;

    public MyClass(EventHub hub)
    {
        _hub = hub;
        _hub.Subscribe<ItemSaved>(this, OnSaved);
    }
    
    public void Dispose() => _hub.Remove(this);
}

but what I really want is the following, as I never need the hub outside of create/delete

class MyClass : IDisposable
{
    public MyClass(EventHub hub)
    {
        hub.Subscribe<ItemSaved>(this, OnSaved);
    }
    
    public void Unsub(EventHub hub) => hub.Remove(this);
}

class MyClass : IDisposable
{
    public MyClass(EventHub hub)
    {
        hub.Subscribe<ItemSaved>(this, OnSaved);
    }
    
    public void Unsub(EventHub hub) => hub.Remove(this);
}

Sossenbinder•16mo ago

You could have your .Subscribe return a delegate which you can store and simply invoke in your dispose So your Subscribe would return a self-cleanup callback If that would make this cleaner But it essentially only removes the need for a _hub = hub Otherwise, the best I can come up with on the spot would be a base class tracking the disposables

Mayor McCheese•16mo ago

I believe the sample I sent you includes method to do what you are trying to accomplish; of course you'll need to adapt to your circumstances however.

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Getting all instances from a IServiceScope