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Open-generic registrations can not be decorated

See original GitHub issue

Let me start by saying that I am quite amazed to see what you’ve been able to build on top of the DI abstraction. The omission of being able to apply decorators (and batch-registration) makes the built-in container IMO a worthless tool for any reasonably sized code base.

That said, I stumbled upon a limitation of your current implementation. Although you’re able to apply open-generic decorators to closed-generic registrations, it seems impossible to apply open-generic decorators to open-generic registrations.

This might very well be a limitation of the API you are building upon, but I’ll let you be the judge of that.

Here’s a failing unit test:

public void CanDecorateOpenGenericTypeBasedOnOpenGenericRegistration()
    var provider = ConfigureProvider(services =>
        services.AddTransient(typeof(IQueryHandler<,>), typeof(QueryHandler<,>));
        services.Decorate(typeof(IQueryHandler<,>), typeof(LoggingQueryHandler<,>));
        services.Decorate(typeof(IQueryHandler<,>), typeof(TelemetryQueryHandler<,>));

    var instance = provider.GetRequiredService<IQueryHandler<MyQuery, MyResult>>();

    var telemetryDecorator = Assert.IsType<TelemetryQueryHandler<MyQuery, MyResult>>(instance);
    var loggingDecorator = Assert.IsType<LoggingQueryHandler<MyQuery, MyResult>>(

Issue Analytics

  • State:closed
  • Created 6 years ago
  • Reactions:3
  • Comments:8 (3 by maintainers)

github_iconTop GitHub Comments

dotnetjunkiecommented, Jun 22, 2021

Any updates here?

@akovanev, Microsoft didn’t add any feature in .NET 5 or .NET 6 to MS.DI that would allow @khellang to implement this feature in Scrutor. That status of this feature request is, therefore, unchanged.

akovanevcommented, Jun 22, 2021

I don’t know if my workaround will be helpful to anyone, as it has a few significant disadvantages, but let me put the link to the project here CqsDecorator.

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