The requested service has not been registered ! AutoFac Dependency Injection

Question

I am simply trying to use AutoFac to resolve dependencies but it throws exception such as

The requested service 'ProductService' has not been registered. To avoid this exception, either register a component to provide service or use IsRegistered()...

class Program
{
    static void Main(string[] args)
    {
        var builder = new ContainerBuilder();

        builder.RegisterType<ProductService>().As<IProductService>();

        using (var container = builder.Build())
        {
            container.Resolve<ProductService>().DoSomething();
        }
    }
}

public class ProductService : IProductService
{
    public void DoSomething()
    {
        Console.WriteLine("I do lots of things!!!");
    }
}

public interface IProductService
{
    void DoSomething();
}

What I have done wrong ?

Solution

With the statement:

builder.RegisterType<ProductService>().As<IProductService>();

Told Autofac whenever somebody tries to resolve an IProductService give them an ProductService

So you need to resolve the IProductService and to the ProductService:

using (var container = builder.Build())
{
    container.Resolve<IProductService>().DoSomething();
}

Or if you want to keep the Resolve<ProductService> register it with AsSelf:

builder.RegisterType<ProductService>().AsSelf();