Question

I need some help – I am trying to use a custom validation attribute in an ASP.NET MVC web project that needs to make a database call.

I have windsor successfully working for the controllers and the IRepository interface is injected normally. The problem arrises when I need to inject the repository into the attribute class.

The attribute class has the following code:

public class ValidateUniqueUrlNodeAttribute : AbstractValidationAttribute
{
    private readonly string message;
    private readonly IArticleRepository articleRepository;

    public ValidateUniqueUrlNodeAttribute(string message)
    {
        this.message = message;
    }

    public ValidateUniqueUrlNodeAttribute(string message, IArticleRepository articleRepository):this(message)
    {
        this.articleRepository = articleRepository;
    }
    public override IValidator Build()
    {
        var validator = new UniqueUrlNodeValidator(articleRepository) { ErrorMessage = message };

        ConfigureValidatorMessage(validator);

        return validator;
    }

My problem is that I cannot seem to make Windsor intercept the contruction of the attribute to pass in the IArticleRepository

The current code in my global.asax file is as follows:

container = new WindsorContainer();
ControllerBuilder.Current.SetControllerFactory(new WindsorControllerFactory(Container));
   container
     .RegisterControllers(Assembly.GetExecutingAssembly())
     .AddComponent<IArticleRepository, ArticleRepository>()
     .AddComponent<ValidateUniqueUrlNodeAttribute>();

Any help would be greatly appreciated.

Answer 1

AFAIK no dependency injection container can directly manage an attribute, since it’s instantiated by the runtime and there’s no way to intercept that.

However, they can cheat by either:

1. Using a static gateway to the container (example), or
2. Using a “BuildUp” feature that injects whatever dependencies are found within an already-constructed object. This is called BuildUp in Unity or InjectProperties in Autofac.

Windsor doesn’t support #2 (ref1, ref2), so you can either:

1. Try one of the hacks to make Windsor support #2 (hack1, hack2)
2. Use a static gateway
3. Implement your own IValidatorBuilder and make it use Windsor to create validators. I’m sure this is implemented somewhere but I can’t find it right now…