19

我有一个动作过滤器检查是否ID设置了会话变量。出于开发目的，我在检查之前手动设置了这个变量。

public class MyActionFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(ActionExecutedContext context)
        {

            context.HttpContext.Session.Add("ID", 123123);

            int ID = (int)context.HttpContext.Session.Contents["ID"];
            var rd = context.HttpContext.Request.RequestContext.RouteData;

            TED _db = new TED();

            //if not in DB
            if (_db.Users.Find(ID) == null && rd.GetRequiredString("action") != "NoAccess")
            {
                RouteValueDictionary redirectTargetDictionary = new RouteValueDictionary();
                redirectTargetDictionary.Add("action", "NoAccess");
                redirectTargetDictionary.Add("controller", "Home");
                redirectTargetDictionary.Add("area", "");

                context.Result = new RedirectToRouteResult(redirectTargetDictionary);
            }

            base.OnActionExecuted(context);
        }
    }

据我了解，此代码在任何页面之前运行，Session["ID"]始终设置。如果我一直在测试，该站点运行良好，但如果我将其放置一段时间然后尝试继续测试，它似乎会中断。这是我得到的错误：

int UserID = (int)Session.Contents["ID"];
System.NullReferenceException: Object reference not set to an instance of an object.

最初我认为会话可能只是到期，但在任何页面加载之前，Session["ID"]应该设置。这里有什么问题？

4

1 回答 1

29

你正在实现你的 actionfilter 的 onOnActionExecuted方法，该方法在你的 action 方法之后执行

您应该实现该OnActionExecuting方法

public class MyActionFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext context)
        {

            context.HttpContext.Session.Add("ID", 123123);

            int ID = (int)context.HttpContext.Session.Contents["ID"];
            var rd = context.HttpContext.Request.RequestContext.RouteData;

            TED _db = new TED();

            //if not in DB
            if (_db.Users.Find(ID) == null && rd.GetRequiredString("action") != "NoAccess")
            {
                RouteValueDictionary redirectTargetDictionary = new RouteValueDictionary();
                redirectTargetDictionary.Add("action", "NoAccess");
                redirectTargetDictionary.Add("controller", "Home");
                redirectTargetDictionary.Add("area", "");

                context.Result = new RedirectToRouteResult(redirectTargetDictionary);
            }

            base.OnActionExecuting(context);
        }
    }
于 2013-02-06T17:39:53.420 回答