Services
Technology Web App Development Mobile App Development Windows App Development Database Development UI/UX Development Cloud Development SEO Digital Marketing Guest Posting Content Writing Artificial Intelligence Data Science ERP Development CRM Development CMS Development LMS Development Business Listing Blockchain Technology Startup Promotion
Products
Data Converter Cleaner TUC - Unit Converter Import Export Survey Manager Tweet Controller
Developer
Article Blog Forum Interview Beginner News Startup Quiz
Users
Career
Apply Job Internship
Pricing
Login Sign Up Get a Quote

forum

home / developersection / forums / what are filters in asp.net mvc/web api? types and use cases?
Ask Question

What are filters in ASP.NET MVC/Web API? Types and use cases?

Anubhav Sharma 444 11 Jun 2025

What are filters in ASP.NET MVC/Web API? Types and use cases?

c# c#api(s)
Updated 18 Jun 2025
Anubhav Sharma
Anubhav Sharma

Student

The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

Message

1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 18 Jun 2025
Report Abuse

In ASP.NET MVC/Web API, filters are attributes that allow you to execute custom logic before or after controller actions run. They are a core part of the request pipeline and are used for cross-cutting concerns like logging, authentication, exception handling, etc.

Filters are declarative attributes applied to controllers or actions to intercept and process HTTP requests/responses at specific points in the execution pipeline.

Types of Filters in ASP.NET MVC / Web API

Filter Type Purpose Runs
Authorization Filter Checks if the user is authorized to access the resource Before controller/action
Action Filter Runs logic before and/or after the action executes Before and after action method
Result Filter Runs logic before and after the response is returned Before and after result execution (e.g., ViewResult)
Exception Filter Handles unhandled exceptions globally When an exception occurs
Authentication Filter (Web API) Authenticates the request Before authorization filter

1. Authorization Filter

Use Case:

  • Role-based access control
  • API key checks

Example:

[Authorize(Roles = "Admin")]
public ActionResult AdminDashboard() { ... }

2. Action Filter

Use Case:

  • Logging, tracking performance
  • Validating input
  • Modifying input/output

Example:

public class LogActionAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Log before action executes
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        // Log after action executes
    }
}

Usage:

[LogAction]
public ActionResult Index() { ... }

3. Result Filter

Use Case:

  • Modify or log response after the action executes but before rendering
  • Add custom headers to response

Example:

public class AddHeaderAttribute : ResultFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        filterContext.HttpContext.Response.Headers["X-App-Version"] = "1.0";
    }
}

4. Exception Filter

Use Case:

  • Global error handling
  • Logging exceptions
  • Showing friendly error pages

Example:

public class CustomExceptionFilter : FilterAttribute, IExceptionFilter
{
    public void OnException(ExceptionContext filterContext)
    {
        // Log or handle exception
        filterContext.ExceptionHandled = true;
    }
}

5. Authentication Filter (Web API only)

Use Case:

  • Custom authentication logic
  • Token or API key authentication

Web API supports IAuthenticationFilter interface (MVC does not have this filter type).

Applying Filters

  • Globally: via FilterConfig.cs
  • Controller-level: on controller class
  • Action-level: on specific action method
// Global
filters.Add(new HandleErrorAttribute());

// Controller-level
[CustomLog]
public class ProductsController : Controller { ... }

// Action-level
[Authorize]
public ActionResult SecureArea() { ... }

Summary

Filter Type Key Use Cases
Authorization User/role validation
Action Logging, timing, input validation
Result Modifying output, headers
Exception Centralized error handling
Authentication (Web API) Token-based or custom authentication
MindStick Training