Autofac: Resolve a specific dependency to a named instance

问题

Using Autofac, I would like to register a component and specify for a specific dependency to be resolved to a named instance.

I found samples like the following using constructor injection which is almost what I want.

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

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

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

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

However, I need this with property injection and I don't want to specify all dependencies.

Something like:

builder.Register<CustomerRepository>().With<IObjectContainer>("CustomerObjectContainer");    
builder.Register<FooRepository>().With<IObjectContainer>("FooObjectContainer");

The build up of all unspecified dependnecies should happen with unnamed instances.

Thanks, Alex

[ADDITION TO THE ANSWER FROM Danielg]

An overload to resolve by type for any property of that type.

    public static IRegistrationBuilder<TLimit, TReflectionActivatorData, TStyle> WithDependency<TLimit, TReflectionActivatorData, TStyle, TProperty>(
        this IRegistrationBuilder<TLimit, TReflectionActivatorData, TStyle> registration,
        Func<IComponentContext, TProperty> valueProvider)
        where TReflectionActivatorData : ReflectionActivatorData
    {
        return registration.WithProperty(new ResolvedParameter((p, c) =>
            {
                PropertyInfo prop;
                return p.TryGetDeclaringProperty(out prop) &&
                    prop.PropertyType == typeof(TProperty);
            },
            (p, c) => valueProvider(c)));
    }

回答1:

I don't think that autofac has a shorthand way of doing this yet, but it is possible with a little effort.

I've written an extension method that does this. Throw it in a static extension class and you should be fine. The extension also shows how to do this the long way.

public static IRegistrationBuilder<TLimit, TReflectionActivatorData, TStyle> WithResolvedProperty<TLimit, TReflectionActivatorData, TStyle, TProperty>(
    this IRegistrationBuilder<TLimit, TReflectionActivatorData, TStyle> registration,
    string propertyName, Func<IComponentContext, TProperty> valueProvider)
        where TReflectionActivatorData : ReflectionActivatorData
{
    return registration.WithProperty(new ResolvedParameter((p, c) =>
                                                               {
                                                                   PropertyInfo prop;
                                                                   return p.TryGetDeclaringProperty(out prop) &&
                                                                          prop.Name == propertyName;
                                                               },
                                                           (p, c) => valueProvider(c)));
}

Don't mind the super long method signature, autofac registrations are very verbose.

You can use the extension like this.

builder.RegisterType<Foo>()
    .WithResolvedProperty("Bar", c => c.Resolve<IBar>());

来源：https://stackoverflow.com/questions/9710779/autofac-resolve-a-specific-dependency-to-a-named-instance

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