代码顺序为：OnAuthorization-->AuthorizeCore-->HandleUnauthorizedRequest

假设AuthorizeCore返回false时，才会走HandleUnauthorizedRequest 方法，而且Request.StausCode会返回401，401错误又相应了Web.config中

的

<authentication mode="Forms">
      <forms loginUrl="~/" timeout="2880" />
    </authentication>

全部，AuthorizeCore==false 时，会跳转到 web.config 中定义的  loginUrl="~/"

 public class CheckLoginAttribute : AuthorizeAttribute
    {

        protected override bool AuthorizeCore(HttpContextBase httpContext)        {
            bool Pass = false;
            if (!CheckLogin.AdminLoginCheck())
            {
                httpContext.Response.StatusCode = 401;//无权限状态码
                Pass = false;
            }
            else
            {
                Pass = true;
            }

            return Pass;
        }

        protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
        {

            if(filterContext.HttpContext.Request.IsAjaxRequest())
            {
                if (!App.AppService.IsLogon)
                {

                    filterContext.Result = new JsonResult
                                               {
                                                   Data = http://www.mamicode.com/new {IsSuccess = false, Message = "不好意思,登录超时,请又一次登录再操作!"},
                                                   JsonRequestBehavior = JsonRequestBehavior.AllowGet
                                               };
                    return;
                }
            }
            if (App.AppService.IsLogon)
            {
                return;
            }

            base.HandleUnauthorizedRequest(filterContext);
            if (filterContext.HttpContext.Response.StatusCode == 401)
            {
                filterContext.Result = new RedirectResult("/");
            }
        }
      

     
    }

AuthorizeAttribute的OnAuthorization方法内部调用了AuthorizeCore方法，这种方法是实现验证和授权逻辑的地方，假设这种方法返回true，

   表示授权成功，假设返回false， 表示授权失败, 会给上下文设置一个HttpUnauthorizedResult，这个ActionResult运行的结果是向浏览器返回

   一个401状态码（未授权）,可是返回状态码没什么意思，一般是跳转到一个登录页面，能够重写AuthorizeAttribute的

   HandleUnauthorizedRequest
protected override void HandleUnauthorizedRequest(AuthorizationContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException("filterContext");
            }
            else
            {
                string path = context.HttpContext.Request.Path;
                string strUrl = "/Account/LogOn?returnUrl={0}";
               
                context.HttpContext.Response.Redirect(string.Format(strUrl, HttpUtility.UrlEncode(path)), true);
               
            }
           
        }