Checking for an attribute in an action filter

Question

In MVC 5, you can do something like this inside an IActionFilter, to check if an attribute has been declared on the the current action (or at controller scope)

public void OnActionExecuting(ActionExecutingContext filterContext)
{
    // Stolen from System.Web.Mvc.AuthorizeAttribute
    var isAttributeDefined = filterContext.ActionDescriptor.IsDefined(typeof(CustomAttribute), true) ||
                             filterContext.ActionDescriptor.ControllerDescriptor.IsDefined(typeof(CustomAttribute), true);

}

So if your controller defines the attribute like so, this works.

[CustomAttribute]
public ActionResult Everything()
{ .. }

Is it possible to do the same in ASP.NET Core MVC (inside an IActionFiler)?

Keep in mind, there is no MVC6, just ASP.NET Core MVC 1.0, 1.1 and 2.0 preview ;) — Tseng
– Tseng, Commented May 26, 2017 at 10:40

Anuraj · Accepted Answer · 2017-05-26 11:02:47Z

26

Yes you can do it. Here is similar code for ASP.NET Core.

public void OnActionExecuting(ActionExecutingContext context)
{
    var controllerActionDescriptor = context.ActionDescriptor as ControllerActionDescriptor;
    if (controllerActionDescriptor != null)
    {
        var isDefined = controllerActionDescriptor.MethodInfo.GetCustomAttributes(inherit: true)
            .Any(a => a.GetType().Equals(typeof(CustomAttribute)));
    }
}

answered May 26, 2017 at 11:02

Anuraj

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2 Comments

Alex from Jitbit Over a year ago

NOTE: this uses reflection. Can be slow! Don't use this answer, look here instead: stackoverflow.com/a/60602828/56621

gerleim Over a year ago

@AlexfromJitbit a bit discorcerning the XML comment on context.ActionDescriptor.EndpointMetadata: "This API is meant for infrastructure and should not be used by application code."

PTD · Accepted Answer · 2021-05-25 10:14:01Z

7

If you need to check the attribute, not only for a method but also for the whole controller in .NET Core, here is how I did it:

var controllerActionDescriptor = actionContext.ActionDescriptor as ControllerActionDescriptor;

if (controllerActionDescriptor != null)
{
    // Check if the attribute exists on the action method
    if (controllerActionDescriptor.MethodInfo?.GetCustomAttributes(inherit: true)?.Any(a => a.GetType().Equals(typeof(CustomAttribute))) ?? false)
        return true;

    // Check if the attribute exists on the controller
    if (controllerActionDescriptor.ControllerTypeInfo?.GetCustomAttributes(typeof(CustomAttribute), true)?.Any() ?? false)
        return true;
}

edited May 25, 2021 at 10:14

PTD

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answered Nov 22, 2019 at 23:07

lisandro101

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Comments

Delmirio Segura · Accepted Answer · 2019-01-31 16:55:01Z

2

Try

if (context.Filters.Any(x => x.GetType() == typeof(Microsoft.AspNetCore.Mvc.Authorization.AllowAnonymousFilter)))
            return;

answered Jan 31, 2019 at 16:55

Delmirio Segura

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