ActionFilter的使用场景及示例

    ActionFilter里面有几个可以重写的事件：OnActionExecuting,OnActionExecuted,OnResultExecuting,OnResultExecuted 从字面我们大概就知道他们运行的顺序了。

    示例：看四个方法的执行次序。定义一个继承ActionFilterAttribute并重写其内部方法的类。

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public class SimpleFilterAttribute:ActionFilterAttribute

    {

        public int ID { get; set; }

        public override void OnActionExecuting(ActionExecutingContext filterContext)

        {

            File.AppendAllText(@"F:/actionlog.txt", this.ID +" "+ "OnActionExecuting <br>");

        }

 

        public override void OnActionExecuted(ActionExecutedContext filterContext)

        {

            File.AppendAllText(@"F:/actionlog.txt", this.ID + " " + "OnActionExecuted  <br>");

        }

 

        public override void OnResultExecuting(ResultExecutingContext filterContext)

        {

            File.AppendAllText(@"F:/actionlog.txt", this.ID + " " + "OnResultExecuting <br>");

        }

 

        public override void OnResultExecuted(ResultExecutedContext filterContext)

        {

            File.AppendAllText(@"F:/actionlog.txt", this.ID + " " + "OnResultExecuted <br>");

        }

    }

 在HomeController的Action方法上面标志。

   [SimpleFilterAttribute(ID=1,Order=1)]
   public ActionResult Index()

执行后，查看actionlog.txt文件可以看到是按照：OnActionExecuting,OnActionExecuted,OnResultExecuting,OnResultExecuted 次序执行的。

    1.OnActionExecuting 
       在Action方法调用前使用，使用场景：如何验证登录等。

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public class LoginFilterAttribute:ActionFilterAttribute

    {

        public override void OnActionExecuting(ActionExecutingContext filterContext)

        {

            //当用户没有验证时

            if (!filterContext.HttpContext.User.Identity.IsAuthenticated)

            {

                

                filterContext.Result = new RedirectToRouteResult("Default",

                    new RouteValueDictionary(new {action="Login"})

                    );

            }

        }

    }

   [LoginFilterAttribute]
    public ActionResult Index()

    2.OnActionExecuted
      在Action方法调用后，result方法调用前执行，使用场景：异常处理

   

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public class ErrorActionFilter:ActionFilterAttribute

    {

        public override void OnActionExecuted(ActionExecutedContext filterContext)

        {

            if (filterContext.Exception != null)

            {

                filterContext.Canceled = true;

                filterContext.Result = new RedirectToRouteResult("Demo", new RouteValueDictionary(new { action = "ErrorPage" }));

            }

        }

    }

       [ErrorActionFilter]
        public void ErrorHandler()
        {
            throw new Exception();
           
        }

    3.OnResultExecuting
     在result执行前发生(在view 呈现前)，使用场景：设置客户端缓存，服务器端压缩.

      明天写一下。

    4.OnResultExecuted
    在result执行后发生，使用场景：异常处理，页面尾部输出调试信息。

    明天写一下。