C Clear Session

Question

Question  1  I want to know when am I supposed to use      Session Abandon      When I use this during tracing and after calling it- I find the session still has a value    And  when am I supposed to use       Session Clear     When should I use each specific method      In general  In my specific case    I check if session is not equal null in Page Load   If session is equal to null  I wanna to clear session and redirect to the login page   Should I use something like this   private void initSession         Session Clear        Session Abandon        Response Redirect  LoginPage aspx

User · Accepted Answer

In ASP NET  when should I use Session Clear   rather than Session Abandon        Session Abandon   destroys the session   and the Session OnEnd event is   triggered       Session Clear   just removes all   values  content  from the Object  The   session with the same key is still   alive       So  if you use Session Abandon    you   lose that specific session and the   user will get a new session key  You   could use it for example when the user   logs out       Use Session Clear    if you want that   the user remaining in the same session    if you don t want him to relogin for   example  and reset all his session   specific data    What is the difference between Session Abandon   and Session Clear       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                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 immediately  Abandon does not    Abandon releases the SessionState object and its items so it can garbage   collected     Clear keeps SessionState and resources associated with it       Session Clear   or Session Abandon         You use Session Clear   when you don t   want to end the session but rather   just clear all the keys in the session   and reinitialize the session       Session Clear   will not cause the   Session End eventhandler in your   Global asax file to execute       But on the other hand   Session Abandon   will remove the   session altogether and will execute   Session End eventhandler       Session Clear   is like removing books   from the bookshelf      Session Abandon   is like throwing the   bookshelf itself    Question  I check on some sessions if not equal null in the page load  if one of them equal null i wanna to clear all the sessions and redirect to the login page   Answer  If you want the user to login again  use Session Abandon

User · Answer

Found this article on net  very relevant to this topic  So posting here     ASP NET Internals - Clearing ASP NET Session variables

User · Answer

The other big difference is Abandon does not remove items immediately  but when it does then cleanup it does a loop over session items to check for STA COM objects it needs to handle specially  And this can be a problem   Under high load it s possible for two  or more  requests to make it to the server for the same session  that is two requests with the same session cookie   Their execution will be serialized  but since Abandon doesn t clear out the items synchronously but rather sets a flag it s possible for both requests to run  and both requests to schedule a work item to clear out session  later   Both these work items can then run at the same time  and both are checking the session objects  and both are clearing out the array of objects  and what happens when you have two things iterating over a list and changing it   Boom  And since this happens in a queueuserworkitem callback and is NOT done in a try catch  thanks MS   it will bring down your entire app domain  Been there

[c#] C# Clear Session

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