Migrating Mvc Dependency Injection

ASP.NET MVC/WebAPI Dependency Injection Migration

Overview

Migrate DependencyResolver-based DI from ASP.NET MVC and WebAPI to ASP.NET Core's built-in IServiceCollection/IServiceProvider pattern, or modernize third-party container integration. ASP.NET Core has DI built into the framework — the DependencyResolver and IDependencyScope APIs no longer exist.

Related skills:

• To remove Autofac entirely and use built-in DI: see migrating-autofac-to-dotnet-di
• To keep Autofac but modernize its integration: see integrating-autofac-with-dotnet

Workflow

Migration Progress:
- [ ] Step 1: Inventory DI usage
- [ ] Step 2: Map service registrations and lifetimes
- [ ] Step 3: Register services in Program.cs
- [ ] Step 4: Migrate or remove third-party container
- [ ] Step 5: Migrate controller factory customizations
- [ ] Step 6: Eliminate Service Locator usage
- [ ] Step 7: Remove obsolete DI code
- [ ] Step 8: Build and verify

Step 1: Inventory DI Usage

Search the project for these patterns to determine the migration scope:

Record every service registration and its lifetime before changing anything.

Step 2: Map Service Registrations and Lifetimes

Document all service registrations from the existing container configuration. Map each lifetime to its ASP.NET Core equivalent:

Per-thread lifetime maps to Scoped because ASP.NET Core processes each request on a single thread from the thread pool, making the semantics equivalent for web scenarios.

Step 3: Register Services in Program.cs

Move all service registrations to builder.Services in Program.cs. Create an extension method to keep Program.cs clean when there are many registrations:

Before (Global.asax.cs or App_Start):

var container = new UnityContainer();
container.RegisterType<IOrderService, OrderService>(new HierarchicalLifetimeManager());
container.RegisterType<IRepository, SqlRepository>(new TransientLifetimeManager());
DependencyResolver.SetResolver(new UnityDependencyResolver(container));

After (Program.cs):

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllersWithViews();
builder.Services.RegisterApplicationServices();

// Extension method in a separate file
public static class ServiceRegistration
{
    public static IServiceCollection RegisterApplicationServices(this IServiceCollection services)
    {
        services.AddScoped<IOrderService, OrderService>();
        services.AddTransient<IRepository, SqlRepository>();
        return services;
    }
}

If HttpContext.Current was used anywhere in the project, register the accessor:

builder.Services.AddHttpContextAccessor();

Step 4: Migrate or Remove Third-Party Container

Choose the appropriate path based on the container in use and the desired outcome.

Option A: Replace with built-in DI (recommended for simple registrations)

Remove the third-party container entirely. Map all registrations to IServiceCollection using the lifetime table in Step 2. Remove all container-specific NuGet packages.

Option B: Keep the third-party container with Core integration

When the project relies on advanced container features (modules, decorators, interceptors, child containers), keep the container but modernize the integration.

Autofac:

// Install: Autofac.Extensions.DependencyInjection
builder.Host.UseServiceProviderFactory(new AutofacServiceProviderFactory());
builder.Host.ConfigureContainer<ContainerBuilder>(containerBuilder =>
{
    containerBuilder.RegisterModule<MyModule>();
});

Unity:

// Install: Unity.Microsoft.DependencyInjection
builder.Host.UseUnityServiceProvider(container =>
{
    container.RegisterType<IMyService, MyService>();
});

Castle Windsor:

// Install: Castle.Windsor.MsDependencyInjection
var windsorContainer = new WindsorContainer();
windsorContainer.Install(FromAssembly.This());
builder.Host.UseServiceProviderFactory(
    new WindsorServiceProviderFactory(windsorContainer));

Ninject: No official ASP.NET Core integration exists. Migrate all registrations to built-in DI (Option A) or switch to Autofac. Do not attempt to create a custom adapter — the IServiceProvider contract has subtleties that break under a naive wrapper.

Step 5: Migrate Controller Factory Customizations

ASP.NET Core replaces both IControllerFactory (MVC) and IHttpControllerActivator (WebAPI) with IControllerActivator.

If the custom factory only existed to enable constructor injection, remove it entirely — ASP.NET Core injects constructor dependencies into controllers by default.

If the factory contains custom logic (e.g., selecting controller types dynamically, applying cross-cutting concerns):

Before (MVC):

public class CustomControllerFactory : DefaultControllerFactory
{
    protected override IController GetControllerInstance(
        RequestContext requestContext, Type controllerType)
    {
        // Custom logic here
        return (IController)_container.Resolve(controllerType);
    }
}

After:

public class CustomControllerActivator : IControllerActivator
{
    public object Create(ControllerContext context)
    {
        var controllerType = context.ActionDescriptor.ControllerTypeInfo.AsType();
        // Custom logic here
        return context.HttpContext.RequestServices.GetRequiredService(controllerType);
    }

    public void Release(ControllerContext context, object controller)
    {
        (controller as IDisposable)?.Dispose();
    }
}

// Register in Program.cs
builder.Services.AddSingleton<IControllerActivator, CustomControllerActivator>();

Step 6: Eliminate Service Locator Usage

Replace all ServiceLocator.Current.GetInstance<T>() calls with constructor injection. The Service Locator pattern hides dependencies and makes testing difficult — ASP.NET Core does not support it.

Before:

public class OrderProcessor
{
    public void Process()
    {
        var service = ServiceLocator.Current.GetInstance<IOrderService>();
        service.Execute();
    }
}

After:

public class OrderProcessor
{
    private readonly IOrderService _orderService;

    public OrderProcessor(IOrderService orderService)
    {
        _orderService = orderService;
    }

    public void Process()
    {
        _orderService.Execute();
    }
}

For locations where constructor injection is not possible (e.g., static methods, legacy code paths that cannot be refactored immediately), inject IServiceProvider and resolve explicitly as a temporary measure:

var service = serviceProvider.GetRequiredService<IOrderService>();

Mark these as technical debt with a TODO comment — they should eventually be refactored to constructor injection.

Step 7: Remove Obsolete DI Code

Remove all Framework-specific DI artifacts:

• DependencyResolver.SetResolver(...) calls
• GlobalConfiguration.Configuration.DependencyResolver = ... assignments
• Custom IDependencyResolver implementations
• Custom IDependencyScope implementations
• ServiceLocator.SetLocatorProvider(...) calls
• CommonServiceLocator package reference
• Third-party container packages (if Option A was chosen in Step 4)

Step 8: Build and Verify

Build the project and verify:

1. All services resolve at startup — missing registrations cause InvalidOperationException at first request
2. Scoped services are not injected into singletons — this is a common lifetime mismatch bug that ASP.NET Core validates by default in Development environment
3. IHttpContextAccessor is registered if any service depends on HttpContext

Property Injection

The built-in container does not support property injection. If the project used property injection (Autofac PropertiesAutowired(), Unity [Dependency] attribute, Ninject [Inject] attribute):

1. Preferred: Convert to constructor injection — add the dependency as a constructor parameter
2. If constructor injection is impractical (e.g., deep inheritance hierarchies): keep a third-party container that supports property injection (Autofac with PropertiesAutowired() works with ASP.NET Core integration)

Success Criteria

• No DependencyResolver, IDependencyScope, or ServiceLocator references remain
• All service lifetimes correctly mapped per the lifetime table
• Third-party container either removed or integrated via UseServiceProviderFactory
• Custom controller factory logic migrated to IControllerActivator or removed
• No property injection without explicit third-party container support
• IHttpContextAccessor registered if HttpContext access is needed outside controllers
• Project builds without errors
• Services resolve correctly at runtime