过滤器其实就是.net中的特性，在.net.35之后我们可以在类或者方法名称上面加某种特性，而在.net mvc环境下，有几个比较重要的特性，如AuthorizeAttribute
它主要有在权限验证上，有时我们习惯叫它“过滤器”，原因是它可以把不符合要求的用户过滤掉，呵呵，下面是系统中常见的用户权限过滤器的代码，供大家学习
1 namespace Web.Attributes 2 { 3 4 /// <summary> 5 /// 用户验证列举 6 /// </summary> 7 public enum AuthenticationType 8 { 9 /// <summary> 10 /// 登录 11 /// </summary> 12 Login, 13 /// <summary> 14 /// 后台登陆 15 /// </summary> 16 BackgroundLogin, 17 /// <summary> 18 /// 注册 19 /// </summary> 20 Register, 21 } 22 23 /// <summary> 24 /// 用户验证过滤器：前台 25 /// </summary> 26 public class UserAuthentication : AuthorizeAttribute 27 { 28 public AuthenticationType Authentication { get; set; } 29 /// <summary> 30 /// 构造函数 31 /// </summary> 32 public UserAuthentication() 33 : this(AuthenticationType.Login) { } 34 public UserAuthentication(AuthenticationType authentication) 35 { 36 this.Authentication = authentication; 37 } 38 /// <summary> 39 /// 执行前验证 40 /// </summary> 41 public override void OnAuthorization(AuthorizationContext filterContext) 42 { 43 44 //验证不成功的时候 45 switch (this.Authentication) 46 { 47 case AuthenticationType.Login: 48 if (!ClientHelper.Current.HasUserInfo) 49 filterContext.Result = new RedirectToRouteResult("Default", new RouteValueDictionary { { "Action", "LogOn" }, { "Controller", "Account" }, { "returnUrl", HttpContext.Current.Request.Url.ToString() } }); 50 break; 51 52 case AuthenticationType.BackgroundLogin: 53 if (string.IsNullOrEmpty(SessionAction.ReadSession("Background_Current_UserID")) || Convert.ToInt32(SessionAction.ReadSession("Background_Current_UserID")) < 0) 54 filterContext.Result = new RedirectToRouteResult("Default", new RouteValueDictionary { { "Action", "LogOn" }, { "Controller", "Account" }, { "returnUrl", HttpContext.Current.Request.Url.ToString() } }); 55 break; 56 case AuthenticationType.Register: 57 filterContext.Result = new RedirectToRouteResult("Default", new RouteValueDictionary { { "Action", "Register" }, { "Controller", "Account" } }); 58 break; 59 default: 60 filterContext.Result = new RedirectToRouteResult("Default", new RouteValueDictionary { { "Action", "Index" }, { "Controller", "Home" } }); 61 break; 62 } 63 64 } 65 } 66 }