Hello and welcome to Code2Night! In today's blog post, we're going to explore the concept of a custom authentication filter in ASP.NET. As developers, we're often tasked with the responsibility of implementing user authentication and validating user authentication for all actions in our web applications. While this process is necessary for ensuring the security and integrity of our applications, it can be time-consuming and cumbersome to implement.

That's where the custom authentication filter comes in. With the help of a custom authentication filter, we can streamline this process and make our code more efficient and secure. Essentially, custom authentication filter allow us to create a reusable component that can be applied to multiple actions in our codebase. This not only reduces duplication and increases code readability but also allows us to centralize our authentication logic and ensure that it's consistent across our entire application.

In this blog post, we'll dive into the details of how custom authentication filter work and how we can create and use them in our ASP.NET applications. We'll start by discussing the basics of user authentication and why it's important for web applications. From there, we'll explain what custom authentication filter are and how they differ from other authentication methods. We'll also cover the different types of custom authentication filter that are available in ASP.NET and how to choose the right one for your application.

Once we've covered the basics, we'll walk through the process of creating a custom authentication filter from scratch. We'll start by creating a new ASP.NET project and adding a basic authentication filter. From there, we'll demonstrate how to customize the filter to fit your specific application's needs. We'll also provide plenty of code examples and best practices to help you get started with your own custom authentication filter implementation.

By the end of this post, you'll have a solid understanding of how to use custom authentication filters to improve the security and efficiency of your web applications. You'll also be equipped with the knowledge and skills needed to create your own custom authentication filter and integrate it into your ASP.NET project. So, let's get started and dive into the world of custom authentication filter in ASP.NET!

Customer Filter Attribute

Attribute filters refer to specific pieces of code which will execute whenever the action will be called on which they are applied. We can create common custom filters and use them for authentication. You have to follow these steps:-

First of all, add one new class file and name it CustomFilter.cs, and copy the code from below

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

namespace CustomFilter.Models
{
    public class AuthenticateUser : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            base.OnActionExecuting(context);
            if (!IsValidLogin())
            {
                context.Result = new RedirectToRouteResult(
                new RouteValueDictionary
                {
                        {"controller", "Users"},
                        {"action", "Login"}
                });
            }
        }

        public bool IsValidLogin()
        {
            if ("Value from cookie"!= "0")
            {
                return true;
            }
            //Add code for User authentication fail here
            return false;
        }
    }
}

Now reference this class in your controller and apply this attribute on the action or controller level as you can see below

You can copy the code from below. You can implement your own logic for validating if a user is logged in or not in the IsValidLogin method in the custom filter class.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using CustomFilter.Models;

namespace CustomFilter.Controllers
{
    [AuthenticateUser] //Use this line to apply authentication on action level
    public class HomeController : Controller
    {
      //  [AuthenticateUser]  //Use this line to apply authentication on action level
        public ActionResult Index()
        {
            return View();
        }

        public ActionResult About()
        {
            ViewBag.Message = "Your application description page.";

            return View();
        }

        public ActionResult Contact()
        {
            ViewBag.Message = "Your contact page.";

            return View();
        }
    }
}

Now, whenever you will call any action having this filter attribute, it will first go to the custom filter and validate the user login. So this is how we can implement Authenticating User Login using the custom filter in Asp.Net MVC.