一直都知道MVC中的ActionFilter,只是没有在实际项目中使用过。
顾名思义，ActionFilter就是指在Action上的Filter, 那么，在Action上的Filter到底有哪些呢。首先我们看看MVC中的Controller基类（抽象类）
?public abstract class Controller : ControllerBase, IActionFilter, IAuthenticationFilter, IAuthorizationFilter, IDisposable, IExceptionFilter, IResultFilter, IAsyncController, IController, IAsyncManagerContainer ???{ ???}我们可以看到，它有5个Filter,分别是IActionFilter, IAuthenticationFilter, IAuthorizationFilter, IExceptionFilter, IResultFilter. 我们先看看第一个IActionFilter
IActionFilter解析
从名称就可以看出，IActionFilter是一个接口.源码如下
???// ???// 摘要: ???// ????Defines the methods that are used in an action filter. ???public interface IActionFilter ???{ ???????// ???????// 摘要: ???????// ????Called after the action method executes. ???????// ???????// 参数: ???????// ??filterContext: ???????// ????The filter context. ???????void OnActionExecuted(ActionExecutedContext filterContext); ???????// ???????// 摘要: ???????// ????Called before an action method executes. ???????// ???????// 参数: ???????// ??filterContext: ???????// ????The filter context. ???????void OnActionExecuting(ActionExecutingContext filterContext); ???}可以看到，该接口中有两个方法，一个是OnActionExecuted (执行完Action之后执行该方法)，另一个是OnActionExecuting(执行Action之前执行该方法)
也就是这两个方法分别在Action的前后执行. 所以它可以用于记录日志，获取action的访问量......
知道了之后，那么我们如何来实现ActionFilter呢。
我们注意到，Controller基类继承了IActionFilter接口，而我们在MVC中写的Controller又都继承自Controller基类, 所以我们应该可以直接在MVC的Controller中override这两个方法
1. 用override的方式来实现ActionFilter
1 ????public class HomeController : Controller 2 ????{ 3 ????????public ActionResult Index() 4 ????????{ 5 ????????????return View(); 6 ????????} 7 ?8 ????????protected override void OnActionExecuting(ActionExecutingContext filterContext) 9 ????????{10 ????????????filterContext.HttpContext.Response.Write("Execute something before action");11 12 ????????????base.OnActionExecuting(filterContext);13 ????????}14 15 ????????protected override void OnActionExecuted(ActionExecutedContext filterContext)16 ????????{17 ????????????filterContext.HttpContext.Response.Write("Execute something after action");18 19 ????????????base.OnActionExecuted(filterContext);20 ????????}21 ????}
这样好像就可以的，但是它有个问题，就是它只能用于HomeController, 有没有一种方法，我能写一个ActionFilter,可以用于多个Controller中的不同Action呢
显然，可以做到。我们可以自己写一个ActionFilter的类，使它继承IActionFilter, 如下：
2. 自定义一个ActionFilter 属性来实现IActionFilter接口
1 ???public class MyActionFilterAttribute : Attribute, IActionFilter 2 ????{ 3 ????????public void OnActionExecuted(ActionExecutedContext filterContext) 4 ????????{ 5 ????????????filterContext.HttpContext.Response.Write("Execute something before action"); 6 ????????} 7 ?8 ????????public void OnActionExecuting(ActionExecutingContext filterContext) 9 ????????{10 ????????????filterContext.HttpContext.Response.Write("Execute something after action");11 ????????}12 ????}好了，到现在我们就有自己写的ActionFilter了，叫做“MyActionFilter”, 如何使用它呢，很简单的
1 ????public class HomeController : Controller2 ????{3 ????????[MyActionFilter]4 ????????public ActionResult Index()5 ????????{6 ????????????return View();7 ????????}8 ????}除了上面两种方法，还有没有其他方法呢。事实上是有的,MVC Framework自己给我们提供了一个ActionFilterAttribute特性，这也是一个抽象类，我们来看看源码
1 ????// 2 ????// 摘要: 3 ????// ????Represents the base class for filter attributes. 4 ????[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = false)] 5 ????public abstract class ActionFilterAttribute : FilterAttribute, IActionFilter, IResultFilter 6 ????{ 7 ????????// 8 ????????// 摘要: 9 ????????// ????Initializes a new instance of the System.Web.Mvc.ActionFilterAttribute class.10 ????????protected ActionFilterAttribute();11 12 ????????//13 ????????// 摘要:14 ????????// ????Called by the ASP.NET MVC framework after the action method executes.15 ????????//16 ????????// 参数:17 ????????// ??filterContext:18 ????????// ????The filter context.19 ????????public virtual void OnActionExecuted(ActionExecutedContext filterContext);20 ????????//21 ????????// 摘要:22 ????????// ????Called by the ASP.NET MVC framework before the action method executes.23 ????????//24 ????????// 参数:25 ????????// ??filterContext:26 ????????// ????The filter context.27 ????????public virtual void OnActionExecuting(ActionExecutingContext filterContext);28 ????????//29 ????????// 摘要:30 ????????// ????Called by the ASP.NET MVC framework after the action result executes.31 ????????//32 ????????// 参数:33 ????????// ??filterContext:34 ????????// ????The filter context.35 ????????public virtual void OnResultExecuted(ResultExecutedContext filterContext);36 ????????//37 ????????// 摘要:38 ????????// ????Called by the ASP.NET MVC framework before the action result executes.39 ????????//40 ????????// 参数:41 ????????// ??filterContext:42 ????????// ????The filter context.43 ????????public virtual void OnResultExecuting(ResultExecutingContext filterContext);44 ????}所以，我们可以写一个自己的ActionFilter属性，来实现MVC Framework提供的这个类ActionFilterAttribute就好
3. 自定义一个ActionFilter 类来继承ActionFilterAttribute类
namespace MyApplication.Controllers{ ???public class HomeController : Controller ???{ ??????[MyActionFilter] ??????public ActionResult Index() ???????{ ???????????return View(); ???????} ???} ???public class MyActionFilterAttribute : ActionFilterAttribute ???{ ???????public override void OnActionExecuting(ActionExecutingContext filterContext) ???????{ ???????????base.OnActionExecuting(filterContext); ???????} ???????public override void OnActionExecuted(ActionExecutedContext filterContext) ???????{ ???????????base.OnActionExecuted(filterContext); ???????} ???}}以上参考 http://www.cnblogs.com/huangxincheng/p/5671106.html
ASP.NET MVC中的ActionFilter介绍学习
原文地址：https://www.cnblogs.com/wphl-27/p/9322792.html