MVC4方法行为过滤器例子(用户登录)

Posted 2020-06-17

在Model文件夹下添加一个类MyActionFilterAttribute继承于ActionFilterAttribute:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MvcValidateDemo.Models
{
    //AllowMultiple = true:允许多个标签同时都起作用
    [AttributeUsage(AttributeTargets.All,AllowMultiple = true)]
    public class MyActionFilterAttribute : ActionFilterAttribute
    {
        public string Name { get; set; }
        //Action执行之前先执行此方法
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            base.OnActionExecuting(filterContext);
            //HttpContext.Current.Response.Write("<br />执行OnActionExecuting方法：" + Name);
            //例子：获取session值，找不到则跳转页面
            string session = HttpContext.Current.Session["user"] == null ? string.Empty : HttpContext.Current.Session["user"].ToString();
            if (string.IsNullOrEmpty(session))
            {
                HttpContext.Current.Response.Redirect("/Home/About");
                return;
            }
        }

        //Action执行之后
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);
            HttpContext.Current.Response.Write("<br />执行OnActionExecuted方法：" + Name);
        }

        //ActionResult执行之前先执行此方法,返回结果前执行方法
        public override void OnResultExecuting(ResultExecutingContext filterContext)
        {
            base.OnResultExecuting(filterContext);
            HttpContext.Current.Response.Write("<br />执行OnResultExecuting方法：" + Name);
        }

        //返回结果后执行方法
        public override void OnResultExecuted(ResultExecutedContext filterContext)
        {
            base.OnResultExecuted(filterContext);
            HttpContext.Current.Response.Write("<br />执行OnResultExecuted方法：" + Name);
        }
    }
}

添加一个控制器：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MvcValidateDemo.Models;

namespace MvcValidateDemo.Controllers
{
    //[MyActionFilter(Name = "HomeController")]  //过滤控制器
    public class HomeController : Controller
    {
        //[MyActionFilter(Name = "Index Action")] //过滤Action
        [MyActionFilter]
        public ActionResult Index()
        {
            //Response.Write("<p>Action执行了</p>");
            //return Content("<br />ok:视图被渲染<br />");
            return View();
        }

        public ActionResult Login()
        {
            Session["user"] = "user";
            return Content("登录成功");
        }

        public ActionResult About()
        {
            return View();
        }

    }
}

当执行Home下Index尝试登录时，会先去执行过滤器的OnActionExecuting方法，过滤器会先判断是否有Session值，如果没找到则跳转页面到/Home/About，当先登录执行/Home/Login时，会将Session值放到服务器中，再次执行/Home/Index则不会跳转