Mastering ASP.NET Web API

Action filters

An Action filter is an attribute that can be applied to a controller or a particular action method.

Action filters implement either the IActionFilter or IAsyncActionFilter interface. They can view and directly modify the result of an action method.

Let's create a simple action filter using the IActionFilter interface. It checks for Header entry publiser-name; if its value does not match Packt, then it returns an action result as BadRequestObjectResult.

Add the CheckPubliserNameAttribute class in ASP.NET Core Web API project. Copy the following code snippet:

 using Microsoft.AspNetCore.Mvc; using Microsoft.AspNetCore.Mvc.Filters; namespace filters_demo { //Action Filter example public class CheckPubliserNameAttribute : TypeFilterAttribute ...