IResultFilter

1、新建类CustomResultFilterAttribute继承Attribute, IResultFilter

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

namespace Project6.Utility.Filters
{
    public class CustomResultFilterAttribute : Attribute, IResultFilter
    {
        public CustomResultFilterAttribute()
        {
            Console.WriteLine("CustomResultFilterAttribute构造方法");
        }
        public void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine("OnResultExecuted");
        }

        public void OnResultExecuting(ResultExecutingContext context)
        {
            if(context.Result is JsonResult)
            {
                JsonResult jsonResult = (JsonResult)context.Result;
                context.Result = new JsonResult(new AjaxResult()
                {
                    Success = true,
                    Message = "OK",
                    Data = jsonResult.Value
                });
            }
        }
    }
}

2、类AjaxResult

namespace Project6.Model
{
    public class AjaxResult
    {
        public bool Success { get; set; }
        public string Message { get; set; }
        public object Data { get; set; }

    }
}

3、新建控制器CustomResultFilterController

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

namespace Project6.Controllers
{
    public class CustomResultFilterController : Controller
    {

        public CustomResultFilterController()
        {
            Console.WriteLine("控制器构造函数被执行");
        }

        [CustomResultFilterAttribute]
        public IActionResult Index()
        {
            return Json(new
            {
                Id = 123,
                Name = "net"
            });
        }
    }
}

4、在各个方法处设置断点，运行程序/CustomResultFilter

可以发现当程序第一次启动的时候CustomResultFilterAttribute的构造方法被执行，只运行一次。

之后运行/CustomResultFilter程序的执行顺序是：

CustomResultFilterController构造方法-->

CustomResultFilterController控制器的Index方法-->执行到return返回结果后执行

CustomResultFilterAttribute.OnResultExecuting-->

CustomResultFilterAttribute.OnResultExecuted

 

结论：IResultFilter在Action输出结果前执行。可以用来对输出结果进行修饰重构。