?

????
如果你發現session突然無理由的丟失，而當你認真的檢查代碼并且排除其它常規可能丟失
的可能性時，你可能會像我一樣，幾乎要接近崩潰~！
后來發現問題出在我用代碼創建一個臨時目錄然后刪除臨時目錄的刪除操作上。

現在和大家分享下：希望對碰到類似釘子的朋友有用。。

說白了session丟失實質就是：應用程序重起！

應用程序什么時候自動重起呢？

請參考：Anand在dotnetindia.com發表的文章

原文引用
{
Why?ASP.NET?Restarts?
Found?this?link?from?one?of?the?blogs?I?was?browsing?today.?This?is?ASP.NET?Forum?post?by?Patrick?Y.?Ng?of?MS.

This?talks?about?both?1.0?and?1.1

This?behaviour?has?been?bugging?lots?of?people.?ASP.Net?will?restart?its?application?for?various?reasons.?All?these?reasons?are?legitimate,?but?the?side?effect?is?that?the?application?will?reset?all?its?cache,?application?state,?and?InProc?session?states.?
You?can?detect?the?restart?of?application?and?worker?process?by?using?the?performance?monitor.?The?counters?to?monitor?are?"ASP.NET\Application?Restarts"?and?"ASP.NET\Worker?Process?Restarts".?

For?worker?process?restart,?ASP.NET?will?write?an?entry?in?the?eventlog?to?explain?why?(logLevel?in?controls?how?often?eventlog?is?written).?

For?application?restart,?however,?in?v1?and?v1.1?there?is?no?easy?way?for?a?customer?to?figure?out?why?a?restart?happened.?

So?by?listing?all?reasons?for?app?restart,?I?hope?I?can?help?some?customers?to?understand?and?avoid?the?restart.?

For?v1?
------?

{
Things?that?causes?application?restart:?

-?The?max?compilation?limit?is?reached?(look?for?numRecompilesBeforeApprestart?in?machine.config)?

-?Physical?application?path?of?the?web?application?has?changed.?

-?Change?in?global.asax?or?one?of?the?included?files?

-?Change?in?machine.config?

-?Change?in?web.config?in?the?app?root?

-?Change?inside?bin?directory?or?its?subdirs?

-?A?directory?is?renamed?to?bin,?or?bin?is?created?

-?Overwhelming?change?notifications?–?too?many?files?are?changed?too?fast?in?one?of?content?directories?–?could?happen?if,?for?example,?files?are?generated?on?the?fly?per?request?

-?Change?in?the?code-access?security?policy?file?
}

-?The?settings?of?various?attributes?in?in?machine.config?affect?the?restart/shutdown?of?the?worker?process?itself.?However,?if?you?use?Windows?2003,?and?(by?default)?you?are?NOT?using?IIS5?isolation?mode,?is?ignored.?Instead,?the?settings?in?"Application?Pools"?in?IIS?manager?is?used.?


For?v1.1?
--------?
The?list?for?v1.1?is?the?same?as?v1,?with?the?following?new?conditions:?

{
-?User?code?called?HttpRuntime.UnloadAppDomain?

-?Any?directory?under?the?web?application?folder?is?renamed?
}
IIS?6.0?
--------?
If?you're?using?IIS?6.0,?and?you're?not?using?IIS?5?compatible?mode,?then?aspnet_wp.exe?will?be?replaced?by?w3svc.exe.?You?may?want?to?go?to?IIS?Manager,?go?to?Application?Pools/DefaultAppPool,?and?see?if?any?of?the?parameters?on?the?Recycling?and?Performance?tabs?are?causing?the?IIS?worker?process?(w3svc.exe)?to?shutdown.?
}

也就是說 asp.net 會監視應用程序目錄，一但有被監視
的動作發生（比如:修改了config、重命名目錄等）應用程序就會自動重起
當然這時你的session一定丟失了。

如果避免不了這種操作（如：重命名目錄）；這里我們可以用cookie存信息或存到數據庫去；

注意：除了以上列出的英文條件外。目錄的刪除操作一定丟失session。asp.net的內部機制對待目錄有點像個守財奴，它死守著目錄，你創建它不會管（往里加），一但創建他就會監視該目錄，若你要刪除或重命名它的（動它的目錄），它就發生重起了。。

轉載于:https://www.cnblogs.com/qqcrazyer/archive/2007/01/27/632075.html

總結

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