Singleton service creating an object that requires a scoped service

Question

Singleton service creating an object that requires a scoped service

David Thielen 3,211

Hi all;

I'm getting a scope error on this:

I use AddDbContextFactory() to get a factory that I then use to get a DbContext. The factory is singleton scoped.

The DbContext constructor requires a service. The required service has session scope (it must). The factory is creating this DbContext.

The DbContext created will have a very short lifespan, and be disposed before the session ends. But the factory does not know that.

In this case, is this a scope exception? That the singleton factory will not allow the DbContext it creates to have a session scoped service in its constructor?

And if so, is there any way around this? I think I can make the DbContextFactory session scoped - but is that a good idea?

Is there a way to load the service other than as a constructor parameter?

The way my code is written, the created DbContext will always have a lifespan within the session scope.

thanks - dave

Anonymous

2023-10-13T07:35:57.0766667+00:00

Hi @David Thielen ,

Could you share more details for me, I guess you have some code, we can give you some suggestions.

Usually I prefer the 2 ways below to implement this.

1.we can use Factory Method or Factory Service

builder.Services.AddSingleton<IMyServiceFactory, MyServiceFactory>();

builder.Services.AddScoped<MySessionScopedService>();

2.Scoped DbContextFactory

builder.Services.AddScoped<IDbContextFactory<MyDbContext>, MyDbContextFactory>();

Waiting for your reply.

Best Regards

Jason
David Thielen 3,211 Reputation points

2023-10-13T15:49:52.52+00:00
@Anonymous It's two very basic questions. I'll ask them a different way:

Can a singleton service create an object that has a session scoped service as a constructor parameter?

Can an IDbContextFactory be added with session scope? And if so, what's the downside of doing so?

thanks - dave
Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2023-10-13T17:02:14.56+00:00
no, by definition a singleton service is only created once, so its constructor is only called once.

sure. typically factories are a singleton, but they don't need to be.

technically you can create a scoped object in a singleton. you need to inject an IServiceProvider into your singleton. using this provider, when you need scoped service, call the provider:

using (var scope = serviceProvider.CreateScope()) { var myService = scope.ServiceProvider.GetRequiredService<IMyService>(); // use myService }

note: this is a different scope than the request scope and should not be returned to the caller (as its disposed by the scope dispose).
David Thielen 3,211 Reputation points

2023-10-13T18:07:57.9366667+00:00

@Bruce (SqlWork.com) That's what I assumed but good to have you verify it - thanks

Your answer

Anonymous

2023-10-13T07:35:57.0766667+00:00

Hi @David Thielen ,

Could you share more details for me, I guess you have some code, we can give you some suggestions.

Usually I prefer the 2 ways below to implement this.

1.we can use Factory Method or Factory Service

builder.Services.AddSingleton<IMyServiceFactory, MyServiceFactory>();

builder.Services.AddScoped<MySessionScopedService>();

2.Scoped DbContextFactory

builder.Services.AddScoped<IDbContextFactory<MyDbContext>, MyDbContextFactory>();

Waiting for your reply.

Best Regards

Jason
David Thielen 3,211 Reputation points

2023-10-13T15:49:52.52+00:00

@Anonymous It's two very basic questions. I'll ask them a different way:

Can a singleton service create an object that has a session scoped service as a constructor parameter?

Can an IDbContextFactory be added with session scope? And if so, what's the downside of doing so?

thanks - dave
Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2023-10-13T17:02:14.56+00:00

no, by definition a singleton service is only created once, so its constructor is only called once.

sure. typically factories are a singleton, but they don't need to be.

technically you can create a scoped object in a singleton. you need to inject an IServiceProvider into your singleton. using this provider, when you need scoped service, call the provider:

using (var scope = serviceProvider.CreateScope()) { var myService = scope.ServiceProvider.GetRequiredService<IMyService>(); // use myService }

note: this is a different scope than the request scope and should not be returned to the caller (as its disposed by the scope dispose).
David Thielen 3,211 Reputation points

2023-10-13T18:07:57.9366667+00:00

@Bruce (SqlWork.com) That's what I assumed but good to have you verify it - thanks

Share via

Singleton service creating an object that requires a scoped service

Your answer