CODEWITHSUNDEEP
c#dependency-injectionunity-container
user278618
user278618

Reputation: 20242

BuildUp doesn't resolve dependency

I'm trying to use Dependency attribute with using RegisterInstance. I've read that If I use RegisterInstance I must use BuildUp method on a instance. Unfortunately it doesn't work in my code. It doesn't resolve Alarm property. When I use my code without RegisterInstance everything is ok, but I need use RegisterInstance. Do I miss something?

EDIT

var container = new UnityContainer();
container.RegisterType<IAlarm, Alarm>();

ICar car = new Car();
container.RegisterInstance<ICar>(car);
var carFromContainer = container.BuildUp<ICar>(container.Resolve<ICar>());
var alarm = carFromContainer.Alarm;

public interface ICar
{
    IAlarm Alarm { get; set; }
}

public class Car : ICar
{
    private IAlarm _alarm;

    [Dependency]
    public IAlarm Alarm
    {
        get { return _alarm; }
        set { _alarm = value; }
    }
}

public interface IAlarm
{
    void Launch();
}

public class Alarm : IAlarm
{
    public void Launch()
    {
        Console.WriteLine("Alarm !");
    }
}

Old example

var container = new UnityContainer();
container.RegisterType<IAlarm, Alarm>();
ICar car = new Car();
container.RegisterInstance<ICar>(car);

//container.RegisterType<ICar, Car>();

var client = new Client(container);
var alarm = client.Car.Alarm;
client.Car.Alarm.Launch();

public class Client
{
    public ICar Car { get; set; }
    public Client(UnityContainer container)
    {
        //Car = container.Resolve<ICar>();
        Car = container.BuildUp<ICar>(container.Resolve<ICar>());
    }
}


public interface ICar
{
    IAlarm Alarm { get; set; }
}

public class Car : ICar
{
    private IAlarm _alarm;

    [Dependency]
    public IAlarm Alarm
    {
        get { return _alarm; }
        set { _alarm = value; }
    }
}

public interface IAlarm
{
    void Launch();
}

public class Alarm : IAlarm
{
    public void Launch()
    {
        Console.WriteLine("Alarm !");
    }
}

Upvotes: 0

Views: 658

Answers (1)

Sebastian Weber
Sebastian Weber

Reputation: 6806

I don't understand your sample code. You new up the Car yourself and register it with the container. Then you tell the container to map IAlarm to the implementing class Alarm. Then you inject the container into your Client which is something that is strongly disencouraged. DI containers should never be referenced outside the Composition root of your application. And then you (ab)use your container as a ServiceLocator (which is considered an anti-pattern in modern application architecture) to resolve ICar and inject some value into a property.

I would recommend you re-think your design instead of looking for a solution to the technical issue you face.

UPDATE

Change your interface definition for ICar and put the DependencyAttribute there and it works.

But I cannot recommend that approach either. DI attributes should not polute your code.

Upvotes: 2

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