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)?

Answer 1

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)));
    }
}

Answer 2

Try

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

Answer 3

If you need to check the attribute 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;
        }