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What is the difference between Session.Abandon() and Session.Clear()

Answer 1

+1 A:

Clearing a session removes the values that were stored there, but you still can add new ones there. After destroying the session you cannot add new values there.

RaYell 2009-09-24 08:46:22

thanks but this works:(inconsistent with your idea)Session.Abandon(); Session["tempKey1"] = "tempValue1"; Response.Write(Session["tempKey1"].ToString());

backdoor 2009-09-24 08:50:48

It does because session will be destroyed after you refresh your page actually. Session id it (usually) stored in a cookie.

RaYell 2009-09-24 08:52:40

i dont understand.i mean after i call Session.Abandon() still i can add values to it. (even if page is posted back and again renders).

backdoor 2009-09-24 09:03:56

You may have you session set to autoregenerate id after it was destroyed. So when you assign a value to destroyed session new session will be generated automatically.

RaYell 2009-09-24 09:25:30

yes, using this session id will regenerate but my question is: what is different between session.clear() and session.abandone() at all.in this way when autoregenerate is seted to false these tow dont differ in anything else raising Sesion_End?

backdoor 2009-09-24 09:29:42

Answer 2

+1 A:

The session data is stored in a file on the server.

Clearing the session will not unset the session, it still exists with the same ID for the user but with the values simply cleared.

Abandon will destroy the session completely, meaning that you need to begin a new session before you can store any more values in the session for that user.

Evernoob 2009-09-24 08:47:58

thanks but this works:(inconsistent with your idea)Session.Abandon(); Session["tempKey1"] = "tempValue1"; Response.Write(Session["tempKey1"].ToString());

backdoor 2009-09-24 08:52:16

Session data is not stored in a file - either:1) In memory (in or our of process) or 2) in an SQL server DB

UpTheCreek 2009-09-24 10:10:15

Answer 3

+2 A:

When you Abandon() a Session, you (or rather the user) will get a new SessionId (on the next request). When you Clear() a Session, all stored values are removed, but the SessionId stays intact.

Hans Kesting 2009-09-24 08:48:53

thanks.but accroding to mattew macdonalds book it can use same session id. i means that if regenerateExpiredSessionId attribute at configuration/system.web/sessionState element in web.config file is false ASP.Net uses old session id

backdoor 2009-09-24 08:54:29

Answer 4

+12 A:

Clear - Removes all keys and values from the session-state collection.

Abandon - removes all the objects stored in a Session. If you do not call the Abandon method explicitly, the server removes these objects and destroys the session when the session times out.
It also raises events like Session_End.

Session.Clear can be compared to removing all books from the shelf, while Session.Abandon is more like throwing away the whole shelf.

You say:

when i Test Session Id Dont makes any change when i Abandone session

This is correct while you are doing it within one request only.
On the next request the session will be different. But the session ID can be reused so that the id will remain the same.

If you will use Session.Clear you will have the same session in many requests.

Generally, in most cases you need to use Session.Clear.
You can use Session.Abandon if you are sure the user is going to leave your site.

So back to the differences:

Abandon raises Session_End request.
Clear removes items immidiately, Abandon does not.
Abandon releases the SessionState object and its items so it can ba garbage collected to free the resources. Clear keeps SessionState and resources associated with it.

Dmytrii Nagirniak 2009-09-24 09:09:49

and if i call session.clear() this you tells accures again. not?(all else raising Session_End event)

backdoor 2009-09-24 09:16:09

Session.Clear will **only** remove items from the Session. Nothing more. You can call it as many times as needed.

Dmytrii Nagirniak 2009-09-24 09:49:20

Added meatphora-comparisson.

Dmytrii Nagirniak 2009-09-24 09:51:29

@AnthonyWJones, you are right "destroy" is incorrect to say. Better is REMOVE objects from session.But Session.Clear also does not destroy objects, it removes thm from session so they can be garbage collected.Also, storing COMPLEX objects is not recommended, otherwise I consider it fine.

Dmytrii Nagirniak 2009-09-24 10:00:41

@Dmitriy: Why "storing COMPLEX objects is not recommended"?

Kamarey 2009-09-24 10:06:12

@Dmitriy: Actually I had confused Session with the classic-asp session where is definitely not a good idea to store objects. I would agree though that complex or rather large objects stored in the session may result in scalability concerns.

AnthonyWJones 2009-09-24 10:10:01

@Kamarey, storing objects in session MIGHT require it to be serialisable. Complex objects might not always be easily (de)serialised. In addition to that (de)serialisation of complex objects is time and resources consumming process. So in short, for performance and scalability reasons

Dmytrii Nagirniak 2009-09-24 10:13:40

@Dmitriy: in this way if object is not disposable what happens?(do not implement IDisposable Interface)it just omits to be garbage collected?you sure?

backdoor 2009-09-24 10:15:07

@Dmitriy: when i call session.abandone() even in next request session ID is same as when sesion is alive.

backdoor 2009-09-24 10:17:03

@backdoor, I have added the explanation to my answer why you can have the same session id. I'll repeat: Session (and therfore its ID) never changes within one request. At the end of the request the session is thrown away. So *next* request will have new session and new id.

Dmytrii Nagirniak 2009-09-24 10:19:23

@Dmitriy: and i tell my friend: when i call session.abandone() even in next request session ID is same as when sesion is alive (last post backs...)

backdoor 2009-09-24 10:22:22

Should not be the case unless browser caches your page or cookie for some reason is not removed: http://technicalsol.blogspot.com/2008/07/understanding-sessionabandon.htmlhttp://bytes.com/topic/asp-classic/answers/470642-session-abandon-not-working

Dmytrii Nagirniak 2009-09-24 10:38:15

Actually the session id can be reused (so you have the same id but different session). I added link to the full explanation to my answer.

Dmytrii Nagirniak 2009-09-24 10:41:21

@ Dmitriy: by default SessionID will reused for creating Session on ASP.Net unless you configure it to dont do this. it means that in default situation session.abandon() and session.clear() have not difference else session.abandon() fires Session_End event..?

backdoor 2009-09-24 11:16:25

No there is a difference. Clear removes all the data from session immidiately and preserves the session for further requests.Abandon removes the items at the end of the request, destoys the current session object. So in case you store session in the database you will end up with a new row for the session. While Clear will still use the same row. That is only ID that can be still the same.

Dmytrii Nagirniak 2009-09-24 12:05:05

tanks i've got it...thus just 2 difference there are: 1- raising Session_End event2- clearing SessionObject at the end of processing page instead of immediatly not?

backdoor 2009-09-24 12:40:12

Updated the answer again. Hope that is more clear.

Dmytrii Nagirniak 2009-09-24 12:58:42

Answer 5

+1 A:

clear-its remove key or values from session state collection..

abandon-its remove or deleted session objects from session..

maxy 2009-09-25 10:47:42

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What is the difference between Session.Abandon() and Session.Clear()

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