Hands-On RESTful Web Services with ASP.NET Core 3

Asynchronous filters

Filters support both asynchronous and synchronous behaviors. As we saw in the previous example, CustomActionFilter implements two synchronous methods: OnActionExecuting and OnActionExecuted. In the case of an asynchronous filter, the implementation is different:

using System.Threading.Tasks;using Microsoft.AspNetCore.Mvc.Filters;namespace SampleAPI.Filters{    public class CustomActionFilterAsync : IAsyncActionFilter    {        public async Task OnActionExecutionAsync(ActionExecutingContext          context, ActionExecutionDelegate next)        {            //Before              var resultContext = await next();             //After        }    }}

CustomActionFilterAsync implements the async version of the action filter class, that is, IAsyncActionFilter, and implements only one method, ...