.net - 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");
}

Answer 1

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.