IAsyncResourceFilter

1、新建一个CustomAsyncResourceFilterAttribute类

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;

namespace Project6.Utility.Filters
{
    public class CustomAsyncResourceFilterAttribute : Attribute, IAsyncResourceFilter
    {
        private static Dictionary<string, object> CacheDictionary = new Dictionary<string, object>();
        public async Task OnResourceExecutionAsync(ResourceExecutingContext context, ResourceExecutionDelegate next)
        {
            Console.WriteLine("Before");
            string key = context.HttpContext.Request.Path;
            if (CacheDictionary.ContainsKey(key))
            {
                context.Result = (IActionResult)CacheDictionary[key];
            }
            else
            {
                //执行控制器的构造函数和Action方法
                ResourceExecutedContext resource = await next.Invoke();
                CacheDictionary[key] = resource.Result;
                Console.WriteLine("After");
            }
        }
    }
}

2、新一个控制器CustomAsyncResourceController

using Microsoft.AspNetCore.Mvc;
using Project6.Utility.Filters;

namespace Project6.Controllers
{
    public class CustomAsyncResourceController : Controller
    {
        
        public CustomAsyncResourceController()
        {
            Console.WriteLine("构造函数被执行");
        }

        [CustomAsyncResourceFilter]
        public IActionResult Index()
        {
            ViewBag.Date = DateTime.Now.ToString("yyyyMMdd HH:mm:ss");
            return View();
        }
    }
}

3、对应的视图

<h1>控制器的时间：@ViewBag.Date</h1>
<h1>视图的时间：@DateTime.Now.ToString("yyyyMMdd HH:mm:ss")</h1>

4、在各个方法处设置断点，运行程序/CustomAsyncResource

可以发现程序的执行顺序是：

OnResourceExecutionAsync-->

ResourceExecutedContext resource = await next.Invoke();

CustomAsyncResourceController构造函数-->

Action方法--->

ResourceExecutedContext resource = await next.Invoke();之后的代码。

 

当第二次运行的时候，程序运行到context.Result = (IActionResult)CacheDictionary[key];直接返回结果不在执行之后的代码

实际可以运用在整个视图的缓存，避免数据库重复查询