C#•2y ago

❔ Strategy for plugin architecture dependency injection

I am creating an application with simple plugins in which registration information of plugins are stored in a database. I am having challenges with dependency injection. Each plugin assembly has the following marker assembly:

 csharp
public interface IPluginRegistrar
{
    IServiceCollection RegisterPluginServices(IServiceCollection services);
}

 csharp
public interface IPluginRegistrar
{
    IServiceCollection RegisterPluginServices(IServiceCollection services);
}

Idea is to call the interface above for each of plugin assemblies stored in the database, but I cannot resolve my plugin DbContext without doing BuildServiceProvider() which I cannot do(or not advised to do) during ConfigureServices(). Is there any strategy or pattern to tackle this?

12 Replies

JakenVeina•2y ago

as in, you need a DbContext to retrieve the info needed to load the plugins?

pirrippuOP•2y ago

Yes exactly like that, and then register services required by the plugins

JakenVeina•2y ago

so, you need a DbContext before your main application IoC container exists so, you can't use the main application IoC container so, you need to create one yourself or create a setup-only IoC container which, BTW, is already a thing

pirrippuOP•2y ago

What do you mean, setup-only IoC container? I make an intermediary ServiceProvider, like a child container?

JakenVeina•2y ago

not sure what you mean by child container but intermediary, sure logically speaking...

var applicationServices = new ServiceCollection();

using(var setupServiceProvider = new ServiceCollection().ConfigureSetup().BuildServiceProvider())
    applicationServices.ConfigureSetup(setupServiceProvider);

using var applicationServiceProvider = applicationServices.BuildServiceProvider();

applicationServiceProvider
    .GetRequiredService<EntryPoint>()
    .Run();

var applicationServices = new ServiceCollection();

using(var setupServiceProvider = new ServiceCollection().ConfigureSetup().BuildServiceProvider())
    applicationServices.ConfigureSetup(setupServiceProvider);

using var applicationServiceProvider = applicationServices.BuildServiceProvider();

applicationServiceProvider
    .GetRequiredService<EntryPoint>()
    .Run();

ASP.NET already provides exactly this setup

pirrippuOP•2y ago

Interesting approach, thanks. That will take care of possible singleton registrations, right? since setupServiceProvider is disposed.

JakenVeina•2y ago

yup you can definitely register all the same stuff for setup that you do for the main app

pirrippuOP•2y ago

holy schomkes, hol 'up I forgot ServiceProvider can be disposed I'll test this one out tomorrow, maybe I just need to sleep on this

JakenVeina•2y ago

arguably shouldn't but definitely can this is how ASP.NET handles configuration IConfiguration instances need to be available during service configuration as well as a bunch of other setup stuff that's the difference between ConfigureHostServices() and ConfigureApplicationServices() scratch that ConfigureHostConfiguration() versus ConfigureAppConfiguration() so, nevermind, ASP.NET doesn't do this already it does something very similar, but for configuration doesn't actually build a full IoC for setup, just a separate ConfigurationBuilder() and IConfiguration conceptually, it's about the same thing, and you can do what I wrote above

pirrippuOP•2y ago

I see, thank you! But what you said above makes a good point, I'll do something similar. Won't hurt me if I make an intermediate and separate IServiceCollection for DbContext and other IOptions I need for plugin configuration

JakenVeina•2y ago

yup

Accord•2y 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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❔ Strategy for plugin architecture dependency injection