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Can I use Fluent Validation with Dependency Injection without having the automatic validation?

I'm using "FluentValidation.DependencyInjectionExtensions" library (Version="11.4.0") for a .Net Core 6 project.
I have my validator registered in my program file:
services.AddScoped<IValidator<SomeModel>, SomeValidator>();
My code is something like this:
[ApiController]
[Route("[controller]")]
public class SomeController : ControllerBase
{
private readonly IValidator<SomeModel> _someValidator;
public SomeController(IValidator<SomeModel> validator)
{
_someValidator = validator ?? throw new ArgumentNullException(nameof(validator));
}
[HttpPost]
public async Task<IActionResult> SetSome([FromBody] SomeModel model)
{
//The SomeValidator is triggered before this, while being injected into the constructure.
ValidationResult validationResult = await _someValidator.ValidateAsync(model);
}
}
public class SomeModel
{
public string Name { get; private set; }
}
public class SomeValidator : AbstractValidator<SomeModel>
{
public SomeValidator(/* Need to use DI here */)
{
RuleFor(x => x.Name).NotEmpty();
}
}
How can I disable the automatic validation?
I was looking for a solution where i didn't have to use FluentValidation.AspNetCore because supposedly is going to be deprecated. The only way I was able to disable the automatic validation was to remove the validator injection and do something like this:
ValidationResult validationResult = await new SomeValidator.ValidateAsync(model);
But has mentioned earlier I wanted to use DI inside my validator without the need to pass the parameters.

How to get dependency injection working with IAsyncAuthorizationFilter in ASP.NET Core

I have implemented the IAsyncAuthorizationFilter interface to a class; in addition, that class is derived from Attribute, so that I can mark controller classes and action methods using it. This works so far; the Task OnAuthorizationAsync(AuthorizationFilterContext context) method is called before the action method, and if the request is not authenticated, an HTTP 401 is returned for the response.
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public sealed class CustomAuthenticationAttribute : Attribute, IAsyncAuthorizationFilter
{
public async Task OnAuthorizationAsync(AuthorizationFilterContext context)
{
...
}
}
This attribute is used as follows...
[CustomAuthenticationAttribute]
public class SomeDataController : Controller
{
[HttpGet]
public async Task GetData()
{
...
}
}
Now, I want to use an application service (which obtains secret private key information required for authentication from a database) and tried to use property injection for that. Injecting dependencies via the ctor is not a good choice here since it´s implemented as an attribute. So I tried...
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public sealed class CustomAuthenticationAttribute : Attribute, IAsyncAuthorizationFilter
{
public IPrivateKeyLookupService KeyService { get; set; }
public async Task OnAuthorizationAsync(AuthorizationFilterContext context)
{
string publicKey = ...
...
var privateKey = await this.KeyService.GetPrivateKeyFrom(publicKey);
...
}
}
...but property injection does not seem to work here. The service is registered with the IoC, but properties do not get wired. This is an ASP.NET Core 1.1 project in which I use Autofac. In the Startup class my ConfigureServices method has something like that...
public void ConfigureServices(IServicesCollection collection)
{
...
var containerBuilder = new ContainerBuilder();
containerBuilder.RegisterType<AuthKeyService>().As<IPrivateKeyLookupService>();
containerBuilder.Populate(services);
this.container = containerBuilder.Build();
}
Does Autofac support auto-wiring for IAsyncAuthorizationFilter types? And if not, how could I polyfill that functionality?

It turned out to be very simple...
In ASP.NET Core there is the TypeFilter attribute which is also a filter that creates another filter (specified by Type) and satisfies its constructor arguments by involving dependency injection.
I changed the implementation of IAsyncAuthorizationFilter; removed the properties and added a ctor instead, because with TypeFilter ctor injection would work now...
public sealed class CustomAuthenticationAttribute : IAsyncAuthorizationFilter
{
private readonly IPrivateKeyLookupService keyService;
public CustomAuthenticationAttribute(
IPrivateKeyLookupService keyService)
{
this.keyService = keyService;
}
public async Task OnAuthorizationAsync(AuthorizationFilterContext context)
{
...
}
}
I also removed inheritance from Attribute because it´s not needed anymore as well as the declaration of the AttributeUsage attribute.
So, I can use my attribute as follows...
[TypeFilter(typeof(CustomAuthenticationAttribute))]
public class SomeDataController : Controller
{
[HttpGet]
public async Task GetData()
{
...
}
}
Passing additional arguments to the filter´s ctor is also possible via the object[] Arguments property of the TypeFilter class.

A normal thing one needs to do is get ISomething that you registered previously, especially when you implement custom attributes bet really anywhere in the HTTP pipeline will work.
Basically what you like to do is get your "hands" on a HttpContext and use the IServiceProvider located in HttpContext.RequestServices
From there it's all easy sailing if you included
using Microsoft.Extensions.DependencyInjection;
Let me demonstrate this in a small sample where I get to the registered IMemoryCache (you need to register it for this to work of course by adding services.AddMemoryCache(); in your startup.cs)
Here is the copy past stuff:
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.DependencyInjection;
public class SomeAttribute : Attribute,IAuthorizationFilter
{
public void OnAuthorization(AuthorizationFilterContext context )
{
IMemoryCache memory= context.HttpContext.RequestServices.GetService<IMemoryCache>();
}
}

Inject service into Action Filter

I am trying to inject a service into my action filter but I am not getting the required service injected in the constructor. Here is what I have:
public class EnsureUserLoggedIn : ActionFilterAttribute
{
private readonly ISessionService _sessionService;
public EnsureUserLoggedIn()
{
// I was unable able to remove the default ctor
// because of compilation error while using the
// attribute in my controller
}
public EnsureUserLoggedIn(ISessionService sessionService)
{
_sessionService = sessionService;
}
public override void OnActionExecuting(ActionExecutingContext context)
{
// Problem: _sessionService is null here
if (_sessionService.LoggedInUser == null)
{
context.HttpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
context.Result = new JsonResult("Unauthorized");
}
}
}
And I am decorating my controller like so:
[Route("api/issues"), EnsureUserLoggedIn]
public class IssueController : Controller
{
}
Startup.cs
services.AddScoped<ISessionService, SessionService>();

Using these articles as reference:
ASP.NET Core Action Filters
Action filters, service filters and type filters in ASP.NET 5 and MVC 6
Using the filter as a ServiceFilter
Because the filter will be used as a ServiceType, it needs to be registered with the framework IoC. If the action filters were used directly, this would not be required.
Startup.cs
public void ConfigureServices(IServiceCollection services) {
services.AddMvc();
services.AddScoped<ISessionService, SessionService>();
services.AddScoped<EnsureUserLoggedIn>();
...
}
Custom filters are added to the MVC controller method and the controller class using the ServiceFilter attribute like so:
[ServiceFilter(typeof(EnsureUserLoggedIn))]
[Route("api/issues")]
public class IssueController : Controller {
// GET: api/issues
[HttpGet]
[ServiceFilter(typeof(EnsureUserLoggedIn))]
public IEnumerable<string> Get(){...}
}
There were other examples of
Using the filter as a global filter
Using the filter with base controllers
Using the filter with an order
Take a look, give them a try and see if that resolves your issue.
Hope this helps.

Global filters
You need to implement IFilterFactory:
public class AuthorizationFilterFactory : IFilterFactory
{
public bool IsReusable => false;
public IFilterMetadata CreateInstance(IServiceProvider serviceProvider)
{
// manually find and inject necessary dependencies.
var context = (IMyContext)serviceProvider.GetService(typeof(IMyContext));
return new AuthorizationFilter(context);
}
}
In Startup class instead of registering an actual filter you register your filter factory:
services.AddMvc(options =>
{
options.Filters.Add(new AuthorizationFilterFactory());
});

One more way for resolving this problem. You can get your service via Context as in the following code:
public override void OnActionExecuting(ActionExecutingContext context)
{
_sessionService = context.HttpContext.RequestServices.GetService<ISessionService>();
if (_sessionService.LoggedInUser == null)
{
context.HttpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
context.Result = new JsonResult("Unauthorized");
}
}
Please note that you have to register this service in Startup.cs
services.AddTransient<ISessionService, SessionService>();

Example
private ILoginService _loginService;
public override void OnActionExecuting(ActionExecutingContext context)
{
_loginService = (ILoginService)context.HttpContext.RequestServices.GetService(typeof(ILoginService));
}
Hope it helps.

After reading this article ASP.NET Core - Real-World ASP.NET Core MVC Filters (Aug 2016) I implemented it like this:
In Starup.cs / ConfigureServices:
services.AddScoped<MyService>();
In MyFilterAttribute.cs:
public class MyFilterAttribute : TypeFilterAttribute
{
public MyFilterAttribute() : base(typeof (MyFilterAttributeImpl))
{
}
private class MyFilterAttributeImpl : IActionFilter
{
private readonly MyService _sv;
public MyFilterAttributeImpl(MyService sv)
{
_sv = sv;
}
public void OnActionExecuting(ActionExecutingContext context)
{
_sv.MyServiceMethod1();
}
public void OnActionExecuted(ActionExecutedContext context)
{
_sv.MyServiceMethod2();
}
}
}
In MyFooController.cs :
[MyFilter]
public IActionResult MyAction()
{
}
Edit: Passing arguments like [MyFilter("Something")] can be done using the Arguments property of the TypeFilterAttribute class: How do I add a parameter to an action filter in asp.net? (rboe's code also shows how to inject things (the same way))

While the question implicitly refers to "filters via attributes", it is still worth highlighting that adding filters "globally by type" supports DI out-of-the-box:
[For global filters added by type] any constructor dependencies will be populated by dependency injection (DI). Adding a filter by type is equivalent to filters.Add(new TypeFilterAttribute(typeof(MyFilter))).
https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-2.2#dependency-injection
With regards to attribute-based filters:
Filters that are implemented as attributes and added directly to controller classes or action methods cannot have constructor dependencies provided by dependency injection (DI). This is because attributes must have their constructor parameters supplied where they're applied. This is a limitation of how attributes work.
https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-2.2#dependency-injection
However, as mentioned in the previous answers to the OP, there are ways of indirection that can be used to achieve DI. For the sake of completeness, here are the links to the official docs:
ServiceFilterAttribute
TypeFilterAttribute
IFilterFactory implemented on your attribute

Custom filter attributes inject dependency

I'musing ASP.NET Web API and I need to have authorization so I've created custom authorization attribute
public class CustomAuthorizationAttribute : AuthorizeAttribute
In order to inject dependency inside constructor I have following :
public CustomAuthorizationAttribute(IAccountBL accountBl)
{
_accountBL = accountBl;
}
In IAccountBL I have method which interacts with database checking if user is authorized to make request.
Inside Member API controller I've register that attribute
[CustomAuthorization]
public class MemberController : ApiController
But I get following error
Project.Account.AccountBL' does not contain a constructor that takes 0 arguments
And if I register it like
[CustomAuthorization(IAccountBL)]
Thank you

Action filters are just attributes. You do not have control over when those attributes are instantiated by the CLR. One possibility is to write a marker attribute:
public class CustomAuthorizationAttribute : Attribute { }
and then the actual action filter:
public class CustomAuthorizationFilter : ActionFilterAttribute
{
private readonly IAccountBL accountBL;
public CustomAuthorizationFilter(IAccountBL accountBL)
{
this.accountBL = accountBL;
}
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (actionContext.ControllerContext.ControllerDescriptor.GetCustomAttributes<CustomAuthorizationAttribute>().Any() ||
actionContext.ActionDescriptor.GetCustomAttributes<CustomAuthorizationAttribute>().Any())
{
// here you know that the controller or action is decorated
// with the marker attribute so that you could put your code
}
}
}
and finally register it as a global action filter:
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
...
IAccountBL accountBL = ...
config.Filters.Add(new CustomAuthorizationFilter(accountBL));
}
}
and finally you could use the marker attribute:
[CustomAuthorization]
public class MemberController : ApiController
{
...
}

You can get dependency in your filter by using extension method GetDependencyScope for class HttpRequestMessage. It's not a canonical way for dependency injection, but can be used as workaround. A basic example may look like this:
public Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
{
var dependencyScope = context.Request.GetDependencyScope();
var dependency = dependencyScope.GetService(typeof (MyDependencyType));
//use your dependency here
}
This method may be used with constructor injection to simplify unit testing:
public class MyAuthenticationFilter : Attribute, IAuthenticationFilter
{
private Func<HttpRequestMessage, MyDependencyType> _dependencyFactory;
public MyAuthenticationFilter() :
this(request => (MyDependencyType)request.GetDependencyScope().GetService(typeof(MyDependencyType)))
{
}
public MyAuthenticationFilter(Func<HttpRequestMessage, MyDependencyType> dependencyFactory)
{
_dependencyFactory = dependencyFactory;
}
public Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
{
var dependencyScope = context.Request.GetDependencyScope();
var dependency = dependencyFactory.Invoke(context.Request);
//use your dependency here
}
public Task ChallengeAsync(HttpAuthenticationChallengeContext context, CancellationToken cancellationToken)
{
throw new NotImplementedException();
}
public bool AllowMultiple { get; private set; }
}

If anyone finds similar issue here's how I manage to solve it.
My custom filter inherits IAutofacAuthorizationFilter. Besides this one you can also inherit IAutofacExceptionFilter and IAutofacActionFilter.
And inside my DI container I've register this filter for each controller I want to use like this
builder.Register(c => new CustomAuthorizationAttribute(c.Resolve<IAccountBL>()))
.AsWebApiAuthorizationFilterFor<MemberController>()
.InstancePerApiRequest();

If you registered your service on the application using any container, it's very easy to get the instance of your service from anywhere in the scope. Just follow the below code to get your service.
var myService = DependencyResolver.Current.GetService(typeof(IMyService)) as IMyService;
Please make sure you have included System.Web.Mvc in the file.
Happy coding!!!

How to use dependency injection with an attribute?

In an MVC project I'm creating I have the following RequirePermissionAttribute that gets put on any action that needs specific permissions (it's been simplified for this example):
public class RequirePermissionAttribute : ActionFilterAttribute, IAuthorizationFilter
{
public Operation Permissions { get; set; }
public RequirePermissionAttribute() { }
public RequirePermissionAttribute(Operation permissions)
{
this.Permissions = permissions;
}
public bool AuthorizeCore(HttpContextBase httpContext)
{
IAuthorizationService authServ = new ASPNETAuthorizationService();
return authServ.Authorize(httpContext);
}
public void OnAuthorization(AuthorizationContext filterContext)
{
Enforce.ArgNotNull(filterContext);
if (this.AuthorizeCore(filterContext.HttpContext))
{
// code snipped.
}
else
{
// code snipped.
}
}
}
So the problem obviously with this is that my authorize attribute has a dependency on the ASPNETAuthorizationService that I created. I can't go the constructor way since attributes are compile-time checked.
One thing to mention, I'm using my own little IoC that I made and it doesn't have support for property injection (yet). Of course, if I did go the property injection route, I'd have to add support for it (which I'd have to do some research on).
What's the best way to inject something into an attribute class?

What's the best way to inject something into an attribute class?
Strictly speaking, we cannot use dependency injection to inject a dependency into an attribute. Attributes are for metadata not behavior. [AttributeSpecification()] encourages this by forbidding reference types as arguments.
What you're probably looking for is to use an attribute and a filter together, and then to inject dependencies into the filter. The attribute adds metadata, which determines whether to apply the filter, and the filter receives the injected dependencies.
How to use dependency injection with an attribute?
There are very few reasons to do this.
That said, if you're intent on injecting into an attribute, you can use the ASP.NET Core MVC IApplicationModelProvider. The framework passes dependencies into the provider's constructor, and the provider can pass dependencies to the attribute's properties or methods.
In your Startup, register your provider.
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Mvc.ApplicationModels;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.TryAddEnumerable(ServiceDescriptor.Transient
<IApplicationModelProvider, MyApplicationModelProvider>());
services.AddMvc();
}
public void Configure(IApplicationBuilder app)
{
app.UseMvc();
}
}
Use constructor injection in the provider, and pass those dependencies to the attribute.
using System.Linq;
using Microsoft.AspNetCore.Mvc.ApplicationModels;
using Microsoft.AspNetCore.Mvc.Routing;
public class MyApplicationModelProvider : IApplicationModelProvider
{
private IUrlHelperFactory _urlHelperFactory;
// constructor injection
public MyApplicationModelProvider(IUrlHelperFactory urlHelperFactory)
{
_urlHelperFactory = urlHelperFactory;
}
public int Order { get { return -1000 + 10; } }
public void OnProvidersExecuted(ApplicationModelProviderContext context)
{
foreach (var controllerModel in context.Result.Controllers)
{
// pass the depencency to controller attibutes
controllerModel.Attributes
.OfType<MyAttribute>().ToList()
.ForEach(a => a.UrlHelperFactory = _urlHelperFactory);
// pass the dependency to action attributes
controllerModel.Actions.SelectMany(a => a.Attributes)
.OfType<MyAttribute>().ToList()
.ForEach(a => a.UrlHelperFactory = _urlHelperFactory);
}
}
public void OnProvidersExecuting(ApplicationModelProviderContext context)
{
// intentionally empty
}
}
Create an attribute with public setters that can receive dependencies.
using System;
using Microsoft.AspNetCore.Mvc.Routing;
public sealed class MyAttribute : Attribute
{
private string _someParameter;
public IUrlHelperFactory UrlHelperFactory { get; set; }
public MyAttribute(string someParameter)
{
_someParameter = someParameter;
}
}
Apply the attribute to a controller or an action.
using Microsoft.AspNetCore.Mvc;
[Route("api/[controller]")]
[MyAttribute("SomeArgument")]
public class ValuesController : Controller
{
[HttpGet]
[MyAttribute("AnotherArgument")]
public string Get()
{
return "Foobar";
}
}
The above demonstrates one way, for the rare use case, that you can inject dependencies into an attribute. If you figure out a valid reason to do this, please post it in the comments.

I originally thought this was not possible, but I stand corrected. Here's an example with Ninject:
http://codeclimber.net.nz/archive/2009/02/10/how-to-use-ninject-to-inject-dependencies-into-asp.net-mvc.aspx
Update 2016-10-13
This is a pretty old question by now, and frameworks have changed quite a bit. Ninject now allows you to add bindings to specific filters based on the presence of specific attributes, with code like this:
// LogFilter is applied to controllers that have the LogAttribute
this.BindFilter<LogFilter>(FilterScope.Controller, 0)
.WhenControllerHas<LogAttribute>()
.WithConstructorArgument("logLevel", Level.Info);
// LogFilter is applied to actions that have the LogAttribute
this.BindFilter<LogFilter>(FilterScope.Action, 0)
.WhenActionHas<LogAttribute>()
.WithConstructorArgument("logLevel", Level.Info);
// LogFilter is applied to all actions of the HomeController
this.BindFilter<LogFilter>(FilterScope.Action, 0)
.WhenControllerTypeIs<HomeController>()
.WithConstructorArgument("logLevel", Level.Info);
// LogFilter is applied to all Index actions
this.BindFilter(FilterScope.Action, 0)
.When((controllerContext, actionDescriptor) =>
actionDescriptor.ActionName == "Index")
.WithConstructorArgument("logLevel", Level.Info);
This is in keeping with the principle, argued by Mark Seeman and by the author of Simple Injector, which is that you should keep the logic of your action filter separate from the custom attribute class.
MVC 5 and 6 also make it far easier to inject values into attributes than it used to be. Still, separating your action filter from your attribute is really the best approach to take.