Database injection into a validation attribute with ASP MVC and Castle Windsor

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.

Community · Accepted Answer · 2017-05-23 12:02:24Z

5

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:

Using a static gateway to the container (example), or
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:

Try one of the hacks to make Windsor support #2 (hack1, hack2)
Use a static gateway
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...

edited May 23, 2017 at 12:02

CommunityBot

11 silver badge

answered Jun 12, 2009 at 16:56

Mauricio Scheffer

100k24 gold badges197 silver badges280 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ruben Bartelink · Accepted Answer · 2016-02-04 19:41:32Z

0

Don't know if this helps, but I subclassed ValidationAttribute to expose a Resolve<T>() method like so:

public abstract class IocValidationAttribute : ValidationAttribute
{
    protected T Resolve<T>()
    {
        return IocHelper.Container().Resolve<T>();
    }
}

Then it can be used in any custom ValidatorAttribute that needs to hit a database:

public class UniqueEmailAttribute : IocValidationAttribute
{
    public override bool IsValid(object value)
    {
        ICustomerRepository customerRepository = Resolve<ICustomerRepository>();

        return customerRepository.FindByEmail(value.ToString()) == null;
    }
}

I think it's a variation of the 'Static Gateway' approach mentioned by Mauricio Scheffer. I don't know if this is a good design or not. I'm not a huge fan of it, I'd rather the dependency was injected more 'elegantly', though I can't use constructor injection obviously, I'd like to use Property injection but can't work out a way to hook into the ASP.NET MVC framework code to do this (I've even pored though the MVC2 source code).

edited Feb 4, 2016 at 19:41

Ruben Bartelink

62.2k32 gold badges196 silver badges266 bronze badges

answered Feb 28, 2010 at 3:17

Sunday Ironfoot

13.1k16 gold badges78 silver badges91 bronze badges

2 Comments

soniiic Over a year ago

Where do you get IocHelper from?

Aran Mulholland Over a year ago

@soniiic looks like an evil static

Community · Accepted Answer · 2017-05-23 12:32:32Z

I was able to wire it up [using Autofac as it happens, but it's just constructor injection via the ASP.NET MVC DependencyResolver] in this answer, enabling one to write:

class MyModel 
{
    ...
    [Required, StringLength(42)]
    [ValidatorService(typeof(MyDiDependentValidator), ErrorMessage = "It's simply unacceptable")]
    public string MyProperty { get; set; }
    ....
}

public class MyDiDependentValidator : Validator<MyModel>
{
    readonly IUnitOfWork _iLoveWrappingStuff;

    public MyDiDependentValidator(IUnitOfWork iLoveWrappingStuff)
    {
        _iLoveWrappingStuff = iLoveWrappingStuff;
    }

    protected override bool IsValid(MyModel instance, object value)
    {
        var attempted = (string)value;
        return _iLoveWrappingStuff.SaysCanHazCheez(instance, attempted);
    }
}

With some helper classes (look over there), you wire it up e.g. in ASP.NET MVC like so in the Global.asax :-

DataAnnotationsModelValidatorProvider.RegisterAdapterFactory(
    typeof(ValidatorServiceAttribute),
    (metadata, context, attribute) =>
        new DataAnnotationsModelValidatorEx(metadata, context, attribute, true));

Community · Accepted Answer · 2017-05-23 12:25:37Z

-1

Hmm.

Can you test the effect of removing the (string message) ctor, and see if that at least forces Castle to use the ctor with the Repostiory ?

Otherwise we call AddComponent(name, type, type). Other than that it really should work...

Also does this hint at my first idea ? How do I use Windsor to inject dependencies into ActionFilterAttributes

edited May 23, 2017 at 12:25

CommunityBot

11 silver badge

answered Jun 12, 2009 at 10:37

penderi

9,1335 gold badges48 silver badges63 bronze badges

2 Comments

David E Over a year ago

Sorry, I can't remove the string CTOR as the attribute looks like this: [ValidateUniqueUrlNode("Please enter a unique Url")] public string UrlNode { get; set; } Should this be different?

penderi Over a year ago

Dahhh. Still scratching head... I'll have a search

Collectives™ on Stack Overflow

Database injection into a validation attribute with ASP MVC and Castle Windsor

4 Answers 4

Comments

2 Comments

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

2 Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related