It’s taken some time and a couple of long Google Groups threads, but with a kick in the right direction from Nick Blumhardt, I’ve got multitenant dependency injection working with Autofac and available as a contributed library.

The basic usage pattern is:

• Determine a strategy by which tenants are identified. That is, which tenant is making a given request? This might come from an environment variable, a request parameter, a role on the user’s principal, or wherever.
• Build up your application container with the default dependency set. For tenants that don’t override anything, they’ll use these defaults.
• Create a multitenant-aware container based on the application defaults. This is where the magic of AutofacContrib.Multitenant comes into play.
• Configure tenant-specific overrides with the multitenant-aware container. Tenants can override things, add new dependencies, or whatever they need to do.
• Resolve everything out of the multitenant-aware container. All of the resolutions will automatically use your tenant identification strategy so you’ll always get a tenant-specific result.

In practice, it looks like something this:

// First, create your application-level defaults using a standard // ContainerBuilder, just as you are used to. var builder = new ContainerBuilder(); builder.RegisterType<Consumer>().As<IDependencyConsumer>().InstancePerDependency(); builder.RegisterType<BaseDependency>().As<IDependency>().SingleInstance(); var appContainer = builder.Build();  // Once you've built the application-level default container, you // need to create a tenant identification strategy. var tenantIdentifier = new MyTenantIdentificationStrategy();  // Now create the multitenant container using the application // container and the tenant identification strategy. var mtc = new MultitenantContainer(tenantIdentifier, appContainer);  // Configure the overrides for each tenant by passing in the tenant ID // and a lambda that takes a ContainerBuilder. mtc.ConfigureTenant('1', b => b.RegisterType<Tenant1Dependency>().As<IDependency>().InstancePerDependency()); mtc.ConfigureTenant('2', b => b.RegisterType<Tenant2Dependency>().As<IDependency>().SingleInstance());  // Now you can use the multitenant container to resolve instances. // Resolutions will be tenant-specific. var dependency = mtc.Resolve<IDependency>();

The usage is very similar to the existing Autofac usage you know and love.

The multitenancy support works for standard non-web/service apps (e.g., console apps or Windows services), ASP.NET web forms and MVC apps, and WCF service apps.

There’s a ton of documentation about how to use the multitenancy that includes sample code snippets.There are also somesample console, WCF, and ASP.NET MVC applications in the source treeso you can see it in action.

It’s not currently out there as a binary, so you’ll have to do a source checkout and compile it manually, but I’m sure it’ll show up soon. It was released as part of AutofacContrib 2.5.1 and is available for download.

We’re looking for early adopters to give us feedback on it. If you try it out, please let us know what you think in the Autofac Google Group. What did you like? What were the pain points? Did you find a scenario that didn’t work? How was the documentation? The more feedback we get, the better we can make it! Thanks!