Filters — authentication, authorization, action, result and exception — ASP.NET MVC 5 (.NET Framework) — Folder Structure, Request Life Cycle and Features

7. Filters — authentication, authorization, action, result and exception

Intermediate★ Must knowLesson 7 of 10

Filter (MVC 5)	Interface	Runs	Built-in examples
Authentication	`IAuthenticationFilter`	First — establishes identity	Custom token checks
Authorization	`IAuthorizationFilter`	Before model binding/action	`[Authorize]`, `[AllowAnonymous]`, `[RequireHttps]`, `[ValidateAntiForgeryToken]`, `[ChildActionOnly]`
Action	`IActionFilter`	Before/after the action method	`[OutputCache]` (also result), custom logging/auditing
Result	`IResultFilter`	Before/after the result executes	Modify view data, timing
Exception	`IExceptionFilter`	When an unhandled exception occurs	`[HandleError]`

csharp

public class LogActionAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext ctx)
        => Trace.WriteLine($"→ {ctx.ActionDescriptor.ControllerDescriptor.ControllerName}.{ctx.ActionDescriptor.ActionName}");
    public override void OnActionExecuted(ActionExecutedContext ctx)
        => Trace.WriteLine($"← done, exception: {ctx.Exception?.Message}");
}

// Registration levels: global (FilterConfig), controller, action
public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new HandleErrorAttribute());          // shows Views/Shared/Error.cshtml when customErrors is On
        filters.Add(new AuthorizeAttribute());            // whole site requires login ([AllowAnonymous] to opt out)
        filters.Add(new LogActionAttribute());
    }
}

Order: authentication → authorization → (model binding) → action filters → action → action filters (after) → result filters → result → result filters (after); exception filters on errors. The Order property and scope (global → controller → action) control ordering.