Action Filter

Action Filter 是可以附加在Action上的标签.

ASP.NET MVC中包括了一些Filter, 如:

OutputCache:一个缓存,在指定时间间隔更新.

HandleError: 处理错误

Authorize: 授权,限制访问.

当然我们也可以创建自定义的filter.

MVC中支持以下四种Filter:

1. Authorization filters – Implements the IAuthorizationFilter attribute.
2. Action filters – Implements the IActionFilter attribute.
3. Result filters – Implements the IResultFilter attribute.
4. Exception filters – Implements the IExceptionFilter attribute.

自定义的过滤器，可以从ActionFilterAttribute继承，它继承于Filter，同时也继承了两个接口：IActionFilter 及 IResultFilter，所以需要同时四个方法：

• OnActionExecuting – This method is called before a controller action is executed.
• OnActionExecuted – This method is called after a controller action is executed.
• OnResultExecuting – This method is called before a controller action result is executed.
• OnResultExecuted – This method is called after a controller action result is executed.

一个记录日志的Action例子：

   1: using System;

   2: using System.Diagnostics;

   3: using System.Web.Mvc;

   4: using System.Web.Routing;

   5:  

   6: namespace MvcApplication1.ActionFilters

   7: {

   8:      public class LogActionFilter : ActionFilterAttribute

   9:      {

  10:           public override void OnActionExecuting(ActionExecutingContext filterContext)

  11:           {

  12:                Log("OnActionExecuting", filterContext.RouteData);       

  13:           }

  14:  

  15:           public override void OnActionExecuted(ActionExecutedContext filterContext)

  16:           {

  17:                Log("OnActionExecuted", filterContext.RouteData);       

  18:           }

  19:  

  20:           public override void OnResultExecuting(ResultExecutingContext filterContext)

  21:           {

  22:                Log("OnResultExecuting", filterContext.RouteData);       

  23:           }

  24:  

  25:           public override void OnResultExecuted(ResultExecutedContext filterContext)

  26:           {

  27:                Log("OnResultExecuted", filterContext.RouteData);       

  28:           }

  29:  

  30:           private void Log(string methodName, RouteData routeData)

  31:           {

  32:                var controllerName = routeData.Values["controller"];

  33:                var actionName = routeData.Values["action"];

  34:                var message = String.Format("{0} controller:{1} action:{2}", methodName, controllerName, actionName);

  35:                Debug.WriteLine(message, "Action Filter Log");

  36:           }

  37:  

  38:      }

  39: }