[c#] Redirect From Action Filter Attribute

What is the best way to do a redirect in an ActionFilterAttribute. I have an ActionFilterAttribute called IsAuthenticatedAttributeFilter and that checked the value of a session variable. If the variable is false, I want the application to redirect to the login page. I would prefer to redirect using the route name SystemLogin however any redirect method at this point would be fine.

Alternatively to a redirect, if it is calling your own code, you could use this:

actionContext.Result = new RedirectToRouteResult(
    new RouteValueDictionary(new { controller = "Home", action = "Error" })
);

actionContext.Result.ExecuteResult(actionContext.Controller.ControllerContext);

It is not a pure redirect but gives a similar result without unnecessary overhead.

It sounds like you want to re-implement, or possibly extend, AuthorizeAttribute. If so, you should make sure that you inherit that, and not ActionFilterAttribute, in order to let ASP.NET MVC do more of the work for you.

Also, you want to make sure that you authorize before you do any of the real work in the action method - otherwise, the only difference between logged in and not will be what page you see when the work is done.

public class CustomAuthorizeAttribute : AuthorizeAttribute
{
    public override void OnAuthorization(AuthorizationContext filterContext)
    {
        // Do whatever checking you need here

        // If you want the base check as well (against users/roles) call
        base.OnAuthorization(filterContext);
    }
}

There is a good question with an answer with more details here on SO.

This works for me (asp.net core 2.1)

using JustRide.Web.Controllers;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;

namespace MyProject.Web.Filters
{
    public class IsAuthenticatedAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            if (context.HttpContext.User.Identity.IsAuthenticated)
                context.Result = new RedirectToActionResult(nameof(AccountController.Index), "Account", null);
        }
    }
}



[AllowAnonymous, IsAuthenticated]
public IActionResult Index()
{
    return View();
}

I am using MVC4, I used following approach to redirect a custom html screen upon authorization breach.

Extend AuthorizeAttribute say CutomAuthorizer override the OnAuthorization and HandleUnauthorizedRequest

Register the CustomAuthorizer in the RegisterGlobalFilters.

public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{

    filters.Add(new CustomAuthorizer());
}

upon identifying the unAuthorized access call HandleUnauthorizedRequestand redirect to the concerned controller action as shown below.

public class CustomAuthorizer : AuthorizeAttribute
{

    public override void OnAuthorization(AuthorizationContext filterContext)
    {
        bool isAuthorized = IsAuthorized(filterContext); // check authorization
        base.OnAuthorization(filterContext);
        if (!isAuthorized && !filterContext.ActionDescriptor.ActionName.Equals("Unauthorized", StringComparison.InvariantCultureIgnoreCase)
            && !filterContext.ActionDescriptor.ControllerDescriptor.ControllerName.Equals("LogOn", StringComparison.InvariantCultureIgnoreCase))
        {

            HandleUnauthorizedRequest(filterContext);

        }
    }

    protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
    {
        filterContext.Result =
       new RedirectToRouteResult(
           new RouteValueDictionary{{ "controller", "LogOn" },
                                          { "action", "Unauthorized" }

                                         });

    }
}

you could inherit your controller then use it inside your action filter

inside your ActionFilterAttribute class:

   if( filterContext.Controller is MyController )
      if(filterContext.HttpContext.Session["login"] == null)
           (filterContext.Controller as MyController).RedirectToAction("Login");

inside your base controller:

public class MyController : Controller 
{
    public void  RedirectToAction(string actionName) { 
        base.RedirectToAction(actionName); 
    }
}

Cons. of this is to change all controllers to inherit from "MyController" class

Try the following snippet, it should be pretty clear:

public class AuthorizeActionFilterAttribute : ActionFilterAttribute
{
  public override void OnActionExecuting(FilterExecutingContext filterContext)
  {
    HttpSessionStateBase session = filterContext.HttpContext.Session;
    Controller controller = filterContext.Controller as Controller;

    if (controller != null)
    {
      if (session["Login"] == null)
      {
        filterContext.Cancel = true;
        controller.HttpContext.Response.Redirect("./Login");
      }
    }

    base.OnActionExecuting(filterContext);
  }
}

Here is a solution that also takes in account if you are using Ajax requests.

using System;
using System.Web.Mvc;
using System.Web.Routing;

namespace YourNamespace{        
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
    public class AuthorizeCustom : ActionFilterAttribute {
        public override void OnActionExecuting(ActionExecutingContext context) {
            if (YourAuthorizationCheckGoesHere) {               
                string area = "";// leave empty if not using area's
                string controller = "ControllerName";
                string action = "ActionName";
                var urlHelper = new UrlHelper(context.RequestContext);                  
                if (context.HttpContext.Request.IsAjaxRequest()){ // Check if Ajax
                    if(area == string.Empty)
                        context.HttpContext.Response.Write($"<script>window.location.reload('{urlHelper.Content(System.IO.Path.Combine(controller, action))}');</script>");
                    else
                        context.HttpContext.Response.Write($"<script>window.location.reload('{urlHelper.Content(System.IO.Path.Combine(area, controller, action))}');</script>");
                } else   // Non Ajax Request                      
                    context.Result = new RedirectToRouteResult(new RouteValueDictionary( new{ area, controller, action }));             
            }
            base.OnActionExecuting(context);
        }
    }
}