Resolve dependency with autofac based on constructor parameter attribute

Question

I\'m using Autofac. I want to inject a different implementation of a dependency based on an attribute I apply to the constructor parameter. For example:

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Answer 1

It sounds like you want to provide different implementations of IObjectContainer to CustomerRepository and FooRepository. If that is the case, attributes might be a thin metal ruler. Instead, I'll show you how I would implement multiple implementations with Autofac.

(Calls such as .ContainerScoped() have been left out for brevity.)

First, register a version of IObjectContainer for each connection string by naming the registrations:

builder
    .Register(c => new ObjectContainer(ConnectionStrings.CustomerDB))
    .As()
    .Named("CustomerObjectContainer");

builder
    .Register(c => new ObjectContainer(ConnectionStrings.FooDB))
    .As()
    .Named("FooObjectContainer");

Then, resolve the specific instances in the repository registrations:

builder.Register(c => new CustomerRepository(
    c.Resolve("CustomerObjectContainer"));

builder.Register(c => new FooRepository(
    c.Resolve("FooObjectContainer"));

This leaves the repositories free of configuration information:

class CustomerRepository
{
    public CustomerRepository(IObjectContainer db) { ... }
}

class FooRepository
{
    public FooRepository(IObjectContainer db) { ... }
}