C# 动作过滤器中的会话变量
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Session variables in action filter
提问by Jeff
I have an action filter checks whether or not a session variable IDis set. For development purposes, I have manually set this variable prior to the check.
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);
}
}
As far as I understand, this code is run prior to any page, this Session["ID"]is always set. The site works fine if I am consistently testing, but it seems to break if I leave it for a while then try to continue testing. Here is the error I get:
据我了解，此代码在任何页面之前运行，这Session["ID"]始终是设置的。如果我一直在测试，该站点就可以正常工作，但是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.
Initially I thought the session may simply be expiring, but prior to any page loading, Session["ID"]should be getting set. What is the issue here?
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？
采纳答案by Dave Alperovich
you're implementing your actionfilter's on OnActionExecutedmethod which executes AFTER your action method
您正在实现您的 actionfilter 的 onOnActionExecuted方法，该方法在您的操作方法之后执行
You should implement the OnActionExecutingmethod
你应该实现这个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);
}
}
